Author name: Prasanna

Environment Class 7 Questions and Answers Provided helps you to answer complex Questions too easily. You can use them while preparing for board exams and all of them are given by subject experts. Reading NCERT Solutions for Class 7 Social Science Geography Chapter 1 Environment familiarizes you with the kind of questions appearing in the board exams. Students are advised to read these solutions on a regular basis to score well.

Environment Class 7 Questions and Answers Geography Chapter 1

Make your learning experience enjoyable by preparing from the quick links available on this page. Use the Class 7 SST Geography Chapter 1 NCERT Solutions and get to know different concepts involved. All the Solutions are covered as per the latest syllabus guidelines. Knowing the NCERT Class 7 Geography Chapter 1 Questions and Answers helps students to attempt the exam with confidence.

Class 7 Geography Chapter 1 NCERT Textbook Questions and Answers

Let’s Recall

Question 1.
What is an ecosystem?

1. What do you mean by natural environment?
2. Which are the major components of the environment?
3. Give four examples of human made environment.
4. What is lithosphere?
5. Which are the two major components of biotic environment?
6. What is biosphere?

Answer:
It is a system formed by the interactions of all living organisms with each other and with the physical and chemical factors of the environment in which they live, all linked by transfer of energy material.

1. Land, water, air, plants and animals comprise the natural environment. Natural environment refers to both biotic and abiotic conditions existing on earth.
2. The major components of environment are:
3. Natural (living things, land, air and water)
4. Human-made (buildings, parks, bridges, roads, monuments, industries)
5. Human (individual, family, community, religion, educational, economic and political situation)
6. Four examples of human-made environments are roads, buildings, parks and bridges.
7. Lithosphere is the solid crust or the hard top layer of the earth. It is made up of rocks and minerals and covered by a thin layer of soil.
8. Plants and animals are the two major components of biotic environment.
9. Plant or animal kingdom together make biosphere or the living world. It is a narrow zone of the earth where land, water and air interact with each other to support life.

Question 2.
Tick the correct answer.
(i) Which is not a natural ecosystem?
(a) Desert
(b)  Aquarium
(c) Forest
Answer:
(b) Aquarium

(ii) Which is not a component of human environment?
(a) Land
(b)  Religion
(c)  Community
Answer:
(a) Land

(iii) Which is a human-made environment?
(a) Mountain
(b) Seas
(c) Road
Answer:
(c) Road

(iv) Which is a threat to environment?
(a) Growing plant
(b) Growing population
(c) Growing crops
Answer:
(b) Growing population

Question 3.
Match the following:

Answer:
1. (d)
2. (a)
3. (b)
4. (c)

Question 4.
Give reasons.
(i) Man modifies his environment
(ii) Plants and animals depend on each other

Answer:
(i) Man modifies his environment as per his/her continence and fulfils his needs. All the natural things such as air, water, minerals etc., are being used by the man not only for fulfilling his needs but also for the wealth. These activities create imbalance in the environment. These activities are very harmful for the living beings. A balance is required between nature and man. The use of environment should be done harmoniously.

(ii) Plants and animals depend on each other for their survival. Plants take oxygen released by the plants through its photosynthesis process and animals eat plants for their nutrition. Plants get manure and carbon dioxide from animals. The relation between plants and animals form ecosystem.

Question 5.
Activity:
Imagine an ideal environment where you would love to live. Draw the picture of your ideal environment.
Answer:
Students discuss with teacher and can write the answer.

Let’s do

Question 6.
Look at your surroundings. Make a list of uses that the land in your neighborhood is being put to.
Answer:
Students discuss with teacher and write the answer.

Question 7.
Where does the water you use in your home and school come from? Make a list of different uses of water in our daily life. Have you seen anyone wasting water? How?
Answer:
Students discuss with teacher and can write the answer.

Question 8.
Observe the sky while coming to school. Make a note whether the day is cloudy, rainy, sunny, foggy etc.
Answer:
Students discuss with teacher and can write the answer.

Question 9.
Sketch or bring photographs of your place like the students in the story.
Answer:
Students discuss with teacher and can write the answer.

Question 10.
Talk to some elderly person in your neighborhood and collect information about-

1. The trees in his/her neighborhood when he/she was your age.
2. The indoor games he/she played.
3. His/her favorite fruit at your age.
4. How did they make themselves comfortable during hot summers and cold winters?

Display your answers on a wall/bulletin board.

Answer:
Students discuss with teacher and can write the answer.

Hope the data shared above regarding the NCERT Class 6 Social Science Geography Chapter 1 Environment PDF has aided in your exam preparation. If you ever need any assistance you can always reach us and our team will guide you at the soonest possibility.

We are Providing NCERT Solutions for Class 9 English Beehive Chapter 1 The Fun They Had by reading this NCERT Solutions for Class 9 English you can get good marks in your Examination.

The Fun They Had NCERT Solutions for Class 9 English Beehive Chapter 1

The Fun They Had NCERT Text Book Questions and Answers

The Fun They Had Thinking About the Text

I. Answer these questions in a few words or a couple of sentences each.

Question 1.
How old are Margie and Tommy?
Answer:
Margie is eleven and Tommy is thirteen-year old.

Question 2.
What did Margie write in her diary?
Answer:
Margie wrote, “Today Tommy found a real book!”

Question 3.
Had Margie ever seen a book before?
Answer:
No, Margie had never seen a book before.

Question 4.
What things about the book did she find strange?
Answer:
Margie found it strange that the words printed on a book stood still instead of moving the way they did on a screen. She also found it odd that the words on a page always remained the same as the first time they were read.

Question 5.
What do you think a telebook is?
Answer:
A book that can be displayed on a screen is called a telebook.

Question 6.
Where was Margie’s school? Did she have any classmates?
Answer:
Margie’s school was in her home itself. It was right next to her bedroom. No, she did not have any classmates.

Question 7.
What subjects did Margie and Tommy learn?
Answer:
Margie and Tommy learnt geography, history and arithmetic.

II. Answer the following with reference to the story.

Question 1.
“I wouldn’t throw it away.”

(a) Who says these words?
Answer:
Tommy said these words.

(b) What does ‘it’ refer to?
Answer:
‘It’ refers to the television screen.

(c) What is it being compared with by the speaker?
Answer:
Tommy is comparing the television screen to the real books. He thought that after reading such books, one would have to throw them away but he would never throw away his telebooks.

Question 2.
“Sure they had a teacher, but it wasn’t a regular teacher. It was a man.”

(a) Who does ‘they’ refer to?
Answer:
They refers to the students who studied in the old kind of schools.

(b) What does ‘regular’ mean here?
Answer:
Here, ‘regular’ refers to the mechanical teachers.

(c) What is it contrasted with?
Answer:
The mechanical teacher is contrasted with the human teachers of the earlier times.

III. Answer each of these questions in a short paragraph (about 30 words).

Question 1.
What kind of teachers did Margie and Tommy have?
Answer:
The teachers of Margie and Tommy were different from the teachers of today. They were robotic teachers. They were confined to study rooms and taught mechanically.

Question 2.
Why did Margie’s mother send for the County Inspector?
Answer:
Margie was working hard in geography under the guidance of the mechanical teacher, but there was no improvement in her performance. It only kept getting worse. So Margie’s mother sent . for the County Inspector to find out the fault and settle it.

Question 3.
What did he do?
Answer:
The County Inspector gave Margie an apple and started working on the mechanical teacher. He took it apart and then checked it. Margie wished that the Inspector would not know how to put the mechanical teacher together again. But he managed to reassemble it. He slowed down the geography sector of the teacher which was geared a little faster for an average ten-year-old.

Question 4.
Why was Margie doing badly in geography? What did the County Inspector do to help her?
Answer:
Margie was doing badly in geography because the geography sector of the mechanical teacher had been geared a little faster. The County Inspector rightly told her that she could not be blamed for her poor performance. The County Inspector slowed down the geography sector of the mechanical teacher to an average ten-year level.

Question 5.
What had once happened to Tommy’s teacher?
Answer:
Once the history sector of Tommy’s teacher had blanked out completely.

Question 6.
Did Margie have regular days and hours for school? If so, why?
Answer:
Yes, Margie had regular days and hours for school. This was because her mother believed that learning at regular hours helped little girls learn better. Her mechanical teacher was also on at the same time every day except Saturday and Sunday.

Question 7.
How does Tommy describe the old kind of school?
Answer:
Tommy describes the old kind of school as a special building where all kids studied together. There were hundreds of students studying and playing together. They used to shout and laugh together in an open yard.

Question 8.
How does he describe the old kind of teachers?
Answer:
According to Tommy, the old kind of teachers were human beings who taught the students inside a special building. The teachers taught the children in groups and gave them homework and asked them questions.

IV. Answer each of these questions in two or three paragraphs (100-150 words).

Question 1.
What are the main features of the mechanical teachers and the schoolrooms that Margie and Tommy have in the story?
Answer:
Margie and Tommy have mechanical teachers in their schools. They do not have separate buildings for their schools. The next room to their bedroom is the schoolroom for them. Their teachers are, in fact, robotic teachers. They have sectors of different subjects having set text, speed and level.

The mechanical teachers have a big screen showing lessons and test papers. There is a slot where each child has to put in his homework and test assignments for evaluation. These teachers could evaluate the assignment in no time. They could tell how a child was performing but could never tell why the child was performing badly.

Question 2.
Why did Margie hate school? Why did she think the old kind of school must have been fun?
Answer:
Margie did not like her school. The room next to her bedroom was her schoolroom where a
robotic teacher used to teach her every day at a fixed time. She did not like taking tests every day. Her robotic teacher was giving her test after test in geography.

Her performance was worsening day by day. She learnt about the old schools from the book found by Tommy. She learnt that the old schools were located in spacious buildings. All the children from the neighbourhood used to go there together. They laughed, shouted and played together. They learnt the same thing and could help one another in their homework. She thought that these schools must have been fun.

Question 3.
Do you agree with Margie that schools today are more fun than the schools in the story. Give reasons for your answer.
Answer:
Yes, I agree with Margie. In the story, there are no schools as such. The room next to their bedroom is their school. They are taught by a mechanical teacher. There are no human feelings. Everything is monotonous. The child has to complete its homework and put it in the slot meant for it in the machine.

But, in the schools today, there are spacious buildings where all the kids from the neighbourhood go together. They are taught by the human teachers. They study and play together. They learn the same things so that they can help one another in their homework.

The Fun They Had Thinking About Language

Question 1.
Find the sentences in the lesson which have the adverbs given in the box below.
Awfully, sorrowfully, completely, loftily, carefully, differently, quickly, nonchalantly
Answer:
They turned the pages, which were yellow and crinkly, and it was awfully funny to read words that stood still instead of moving the way they were supposed to – on a screen, you know.

The mechanical teacher had been giving her test after test in geography and she had been doing worse and worse until her mother had shaken her head sorrowfully and sent for the County Inspector.

They had once taken Tommy’s teacher away for nearly a month because the history sector had blanked out completely.

He added loftily, pronouncing the word carefully, “Centuries ago.”
“But my mother says a teacher has to be adjusted to fit the mind of each boy and girl it teaches and that each kid has to be taught differently.”
“I didn’t say I didn’t like it,” Margie said quickly.
“May be,” lie said nonchalantly.

Question 2.
Now use these adverbs to fill in the blanks in the sentences below.

• The report must be read carefully so that performance can be improved.
• At the interview, Sameer answered our questions loftily, shrugging his shoulders.
• We all behave differently when we are tired or hungry.
• The teacher shook her head sorrowfully when Ravi lied to her.
• I completely forgot about it.
• When I complimented Revathi on her success, she just smiled nonchalantly and turned away.
• The President of the Company is awfully busy and will not be able to meet you.
• I finished my work quickly so that I could go out to play.

Question 3.
Make adverbs from these adjectives.

(i) angry
(ii) happy
(iii) merry
(iv) sleepy
(v) easy
(vi) noisy
(vii) tidy
(viii) gloomy
Answer:
(i) angrily
(ii) happily
(iii) merrily
(iv) sleepily
(v) easily
(vi) noisily
(vii) tidily
(viii) gloomily

II. Complete the following conditional sentences. Use the correct form of the verb.
1. If I don’t go to Anu’s party tonight,
Answer:
If I don’t go to Anu’s party tonight, she will be angry.

Question 2.
If you don’t telephone the hotel to order food,
Answer:
If you don’t telephone the hotel to order food, you will miss your evening meal.

Question 3.
Unless you promise to write back, I
Answer:
Unless you promise to write back, I will not write to you.

Question 4.
If she doesn’t play any games,
Answer:
If she doesn’t play any games, she will become dull and lazy.

Question 5.
Unless that little bird flies away quickly, the cat
Answer:
Unless that little bird flies away quickly, the cat will pounce on it.

The Fun They Had NCERT Workbook Questions

Question 1.
Go back to the chapter ‘The Fun They Had’ given In your textbook, Beehive, and identity words that
mean the following. The paragraph numbers are given in brackets.
(a) sadly (3) …………
(b) unfamiliar (7) ……….
(c) quite likely (8) …………….
(d) in a casual, calm and relaxed manner (9) …………..
(e) something becoming and shining (10) …………..
Answer:
(a) sorrowfully
(b) strange
(c) probably
(d) nonchalantly
(e) flashing

Question 2.
Find the odd one out.
(a) pleasure, misery, happiness, delight ………….
(b) note, diary, book, copy ……………
(c) TV, computer, mobile, scanner ………….
(d) display, exhibit, appear, show ……….
(e) scornful; contemptuous, mocking, diversity………………
(f) illuminating, gladdening, pleasing, gratifying ………….
Answer:
(a) misery
(b) note
(c) TV
(d) appear
(e) diversity
(f) illuminating

Question 3.
You would have come across the use of prefixes like ‘dis’, ‘un’, ‘mis’, ‘in’, etc., to make opposite words. For example, ‘consolate — disconsolate’. Write the opposites of the following.
(a) use ………..
(b) agree ………..
(c) engage ………..
(d) understand ………..
(e) fold ………..
(f) spell ………..
(g) connect ………..
(h) like ………..
(I) visible ………..
(j) predictable ………..
Answer:
(a) misuse
(b) disagree
(c) disengage
(d) misunderstand
(e) unfold
(f) misspell
(g) disconnect
(h) dislike
(i) invisible
(j) unpredictable

Question 4.
The suffixes are used to get adjective form of the words.
(Example: danger — dangerous). Use the correct suffix to the following to make adjectives.
(a) comfort………………..
(b) sun ………………..
(c) read ………………..
(d) beauty ………………..
(e) enjoy ………………..
(f) suit………………..
(g) help ………………..
(h) use ………………..
(i) hazard ………………..
(j) impress ………………..
Answer:
(a) comfortable
(b) sunny
(c) readable
(d) beautiful
(e) enjoyable
(f) suitable
(g) helpful
(h) useful
(i) hazardous
(j) impressive

Detailed, Step-by-Step NCERT Solutions for Class 10 Sanskrit Shemushi Chapter 1 शुचिपर्यावरणम् Questions and Answers were solved by Expert Teachers as per NCERT (CBSE) Book guidelines covering each topic in chapter to ensure complete preparation.

Shemushi Sanskrit Class 10 Solutions Chapter 1 शुचिपर्यावरणम्

अभ्यासः

प्रश्न 1.
अधोलिखितानां प्रश्नानाम् उत्तराणि संस्कृतभाषया लिखत –

(क) कविः किमर्थं प्रकृतेः शरणम् इच्छति?
उत्तर:
नगरे (अत्र) जीवितं दुर्वहं जातं” अतः कविः प्रकृतेः शरणम् इच्छति।

(ख) कस्मात् कारणात् महानगरेषु संसरणं कठिनं वर्तते?
उत्तर:
यानानां पङक्तयः अनन्ताः अतः महान-गरेषु संसरणं कठिनं वर्तते।

(ग) अस्माकं पर्यावरणे किं किं दूषितम् अस्ति?
उत्तर:
अस्माकम् पर्यावरणे वायुमण्डल, जलं, धरातलम् च दूषितम् अस्ति।

(घ) कविः कुत्र सञ्चरणं कर्तुम् इच्छति?
उत्तर:
कविः एकान्ते कान्तारे सञ्चरणं कर्तुम् इच्छति।

(ङ) स्वस्थजीवनाय कीदृशे वातावरणे भ्रमणीयम्?
उत्तर:
स्वस्थ जीवनाय शुचि वातावरणे भ्रमणीयम्।

(च) अन्तिमे पद्यांशे कवेः का कामना अस्ति?
उत्तर:
अंतिमें पद्यांशे कवे मानवाय जीवनं कामये।

प्रश्न 2.
सन्धि/सन्धिविच्छेदं कुरुत –

(क) प्रकृतिः + ………………….. – प्रकृतिरेव
उत्तर:
प्रकृतिः + एव – प्रकृतिरेव

(ख) स्यात् + …….. + …….. – स्यान्नैव
उत्तर:
स्यात् + न + एव – स्यान्नैव

(ग) ……… + अनन्ताः – ह्यनन्ता:
उत्तर:
हि + अनन्ताः – ह्यनन्ताः

(घ) बहिः + अन्तः + जगति – …………..
उत्तर:
बहिः + अन्तः + जगति – बहिरन्तर्जगति

(ङ) ……… + नगरात् = अस्मान्नगरात्
उत्तर:
अस्मात् + नगरात् = अस्मान्नगरात्

(च) सम् + चरणम् = ……………
उत्तर:
सम् + चरणम् = सञ्चरणम्

(छ) धूमम् + मुञ्चति = …………..
उत्तर:
धूमम् + मुञ्चति = धूमं मुञ्चति

प्रश्न 3.
अधोलिखितानाम् अव्ययानां सहायतया रिक्तस्थानानि पूरयत –
भृशम्, यत्र, तत्र, अत्र, अपि, एव, सदा, बहिः

(क) इदानीं वायुमण्डलं ……………. प्रदूषितमस्ति।
उत्तर:
इदानीं वायुमण्डलं भृशम प्रदूषितमस्ति।

(ख) …………… जीवनं दुर्वहम् अस्ति।
उत्तर:
अत्र जीवनं दुर्वहम् अस्ति।

(ग) प्राकृतिक वातावरणे क्षणं सञ्चरणम् ……….. लाभदायकं भवति।
उत्तर:
प्राकृतिक वातावरणे क्षणं सञ्चरणम् अपि लाभदायक भवति।

(घ) पर्यावरणस्य संरक्षणम् ……….. प्रकृतेः आराधना।
उत्तर:
पर्यावरणस्य संरक्षणम् एव प्रकृते: आराधना।

(ङ) …………….. समयस्य सदुपयोगः करणीयः।
उत्तर:
सदा समयस्य सदुपयोगः करणीयः।

(च) भूकम्पित-समये …………….. गमनमेव उचितं भवति।
उत्तर:
भूकम्पित-समये बहिः गमनमेव उचितं भवति।

(छ) ……………….. हरीतिमा ……………… शुचि पर्यावरणम्। उत्तराणि
उत्तर:
यत्र हरीतिमा तत्र शुचि पर्यावरणम्।

प्रश्न 4.
उदाहरणमनुसृत्य अधोलिखित-पदेषु प्रकृतिप्रत्ययविभाग/संयोगं कुरुत –

यथा-जातम् = जन् + क्त

(क) प्र + कृ + क्तिन्
उत्तर:
प्र + कृ + क्तिन् – प्रकृतिः

(ख) नि + सृ + क्त + टाप् = ……………..
उत्तर:
नि + सु + क्त + टाप् – निस्ता

(ग) ……………… + क्त -दुषितम
उत्तर:
दूष + क्त – दूषितम्

(घ) ……………. + ……………. – करणीयम्
उत्तर:
कृ + अनीयर – करणीयम्

(ङ) …………….. + यत् – भक्ष्यम्
उत्तर:
भक्ष् + यत् – भक्ष्यम्

(च) रम् + ……………….. + ……………… = रमणीया
उत्तर:
रम् + अनीयर + टाप = रमणीया

(छ) ………….. – वरणीया
उत्तर:
व + अनीयर + टाप – वरणीया

(ज) पिष् + ……… – पिष्टाः
उत्तर:
पिष् + क्त = पिष्टाः

प्रश्न 5.
(अ) अधोलिखितानां पदानां पर्यायपदं लिखत –

(क) सलिलम्
उत्तर:
सलिलम् – जलम्

(ख) आम्रम्
उत्तर:
आम्रम् – रसालम

(ग) वनम्
उत्तर:
वनम् – अरण्यम्

(घ) शरीरम्
उत्तर:
शरीरम् – देहम्

(ङ) कुटिलम्
उत्तर:
कुटिलम् – वक्रम

(च) पाषाण:
उत्तर:
पाषाणः – प्रस्तरम्

प्रश्न 5.
(आ) अधोलिखितपदानां विलोमपदानि पाठात् चित्वा लिखत –

(क) सुकरम्
उत्तर:
सुकरम् – दुष्करम्

(ख) दूषितम्
उत्तर:
दूषितम् – शुद्धम्

(ग) गृहणन्ती
उत्तर:
गृहणन्ती – व्यजन्ती

(घ) निर्मलम्
उत्तर:
निर्मलम् – दृषितम्

(ङ) दानवाय
उत्तर:
दानवाय – देवाय

(च) सान्ता:
उत्तर:
सान्ताः – कोलहलः

प्रश्न 6.
उदाहरणमनुसृत्य पाठात् चित्वा च समस्तपदानि समासनाम च लिखत –

यथा-विग्रह पदानि समस्तपद : समासनाम

(क) मलेन सहितम् समलम् अव्ययीभाव
(ख) हरिता: च ये तरवः (तेषां)
(ग) ललिताः च याः लताः (तासाम्) ……
(घ) नवा मालिका ……………..
(ङ) धृतः सुखसन्देशः येन (तम्) ….
(च) कज्जलम् इव मलिनम् (छ) दुर्दान्तैः दशनैः
उत्तर:
समस्तपद : समासनाम
(क) समलम् : अव्यीभाव
(ख) हरिततरूणाम् : कर्मधारय
(ग) लालितलतानाम् : कर्मधारय
(घ) नवमालिका : कर्मधारय
(ङ) धृतसुखसन्देशम् : बहुब्रीहि
(च) कज्जलमलिनं : कर्मधारय
(छ) दुर्दान्तदशनै : कर्मधारय

प्रश्न 7.
रेखाङ्कित-पदमावृत्य प्रश्ननिर्माण कुरुत –

(क) शकटीयानम् कज्जलमलिन धूम मुञ्चति।
उत्तर:
शकटीयानम् कीदृशं धूमं मुञ्चति?

(ख) उद्याने पक्षिणा कलरव चेतः प्रसादयति।
उत्तर:
उद्याने केषाम् कलरवं चेतः प्रसादयति?

(ग) पाषाणीसभ्यतायां लतातरुगुल्माः प्रस्तरतले पिष्टाः सन्ति ।
उत्तर:
पाषाणीसभ्यतायां के प्रस्तरतले पिष्टाः सन्ति?

(घ) महानगरेषु वाहनानाम् अनन्ताः पङ्क्तयः धावन्ति।
उत्तर:
कुत्र वाहनानाम् अनन्ताः पङ्क्तयः धावन्ति?

(ङ) प्रकृत्याः सन्निधौ वास्तविकं सुखं विद्यते।
उत्तर:
कस्याः सन्निधौ वास्तविक सुखं विद्यते?

अन्य परीक्षा उपयोगी पटनाः

प्रश्न 1.
रेखाङ्कितपदानि आधृत्य प्रश्नानिर्माण कुरूत
(रेखांकित पदों के आधार पर प्रश्न निर्माण कीजिए।)

(क) जीवितरसहरणं नो कुर्यात्।
उत्तर:
किम् नो कुर्यात्?

(ख) माम् अस्मात् नगरात् दूर नय।
उत्तर:
माम् कस्मात् नगरात् दूरं नय?

(ग) धरातल समलं जातम्।
उत्तर:
धरातलं कीदृशम् जातम्?

(घ) वाष्पयानमाला संधावति।
उत्तर:
का संधावति?

(ङ) महानगरमध्ये कालायसचक्र भ्रमति।
उत्तर:
कुत्र कालायसचक्र भ्रमति?

प्रश्न 2.
प्रस्तुत पाठं पठित्वा अधोलिखित प्रश्नानां उत्तराणि ‘लिखत
(प्रस्तुत पाठ को पढ़कर निम्नलिखित प्रश्नों के उत्तर लिखि)

I. एकपदेन उत्तरत

(क) शतशकटीयानं कीदृशं धूम मुञ्चति?
उत्तर:
कज्जलमलिनम्

(ख) यानानां कति पङ्कतयः?
उत्तर:
अनन्ताः

(ग) भृशं दूषितं किम्?
उत्तर:
वायुमण्डलम

(घ) नगरात् दूर के नय?
उत्तर:
माम

(ङ) समीरचालिता का?
उत्तर:
कुसुमावलिः।

II. पूर्णवाक्येन उत्तरत –

(क) के पिष्टाः नो भवन्तु?
उत्तर:
प्रस्तरतले लतातरुगुल्माः पिष्टाः नो भवन्तु।

(ख) बन्धो! कुत्र चल?
उत्तर:
बन्धो! खगकुल-कलरव-गुज्जित-वनदेशं चला

(ग) अत्र धरातलं कीदृशम् अभवत्?
उत्तर:
अत्र धरातलं समलम् अभवत्।

(घ) बहिरन्तर्जगति कि करणीयम्?
उत्तर:
बहिरन्तर्जगति बहु शुद्धीकरण करणीयम्?

(ङ) नामान्ते किं प्रपश्चामि?
उत्तर:
ग्रामान्ते निर्झर-नदी-पयः प्रपश्चामि?

योग्यताविस्तारः

समास – समसनं समासः

समास का शाब्दिक अर्थ होता है-संक्षेप। दो या दो से अधिक शब्दों के मिलने से जो नया और संक्षिप्त रूप बनता है वह समास कहलाता है। समास के मुख्यत: चार भेद हैं
1. अव्ययीभाव समास
2. तत्पुरुष
3. बहुव्रीहि
4. द्वन्द्व

1. अव्ययीभाव
इस समास में पहला पद अव्यय होता है और वही प्रधान होता है और समस्तपद अव्यय बन जाता है। यथा-निर्मक्षिकम्-मक्षिकाणाम् अभावः।।
यहा! प्रथमपद निर् है और द्वितीयपद मक्षिकम् है। यहा! मक्षिका की प्रधानता न होकर मक्षिका का अभाव प्रधान है, अतः यहा! अव्ययीभाव समास है। कुछ अन्य उदाहरण देखें

1. उपग्रामम् – ग्रामस्य समीपे – (समीपता की प्रधानता)
2. निर्जनम् – जनानाम् अभावः – (अभाव की प्रधानता)
3. अनुरथम् – रथस्य पश्चात् – (पश्चात् की प्रधानता)
4. प्रतिगृहम् – गृहं गृहं प्रति – (प्रत्येक की प्रधानता)
5. यथाशक्ति – शक्तिम् अनतिव्य – (सीमा की प्रधानता)
6. सचव्म् – चक्रेण सहितम् – (सहित की प्रधानता)

2. तत्पुरुष – ‘प्रायेण उत्तरपदप्रधानः तत्पुरुषः’ इस समास में प्रायः उनरपद की प्रधानता होती है और पूर्व पद उनरपद के विशेषण का कार्य करता है। समस्तपद में पूर्वपद की विभक्ति का लोप हो जाता है।
यथा- राजपुरुषः अर्थात् राजा का पुरुष। यहां! राजा की प्रधानता न होकर पुरुष की प्रधानता है।

1. ग्रामगतः – ग्रामं गतः।
2. शरणागतः – शरणम् आगतः।
3. देशभक्तः – देशस्य भक्तः।
4. सिंहभीतः – सिंहात् भीतः।
5. भयापा: – भयम् आपाः।
6. हरित्रातः – हरिणा त्रात:।
   तत्पुरुष समास के दो प्रमुख भेद हैं-कर्मधारय और द्विगु।

(क) कर्मधारय-इस समास में एक पद विशेष्य तथा दूसरा पद पहले पद का विशेषण होता है। विशेषण विशेष्य भाव के अतिरिक्त उपमान उपमेय भाव भी कर्मधारय समास का लक्षण है।
यथा
पीताम्बरम् – पीतं च तत् अम्बरम्।
महापुरुषः – महान् च असो पुरुषः।
कज्जलमलिनम् – कज्जलम् इव मलिनम्।
नीलकमलम् – नीलं च तत् कमलम्।
मीननयनम् – मीन इव नयनम्।
मुखकमलम् – कमलम् इव मुखम्।

(ख) द्विगु – ‘संख्यापूर्वो द्विगुः’ इस समास में पहला पद संख्यावाची होता है और समाहार (एकत्रीकरण या समूह) अर्थ की प्रधानता होती है।
यथा- त्रिभुजम् – त्रयाणां भुजानां समाहारः। इसमें पूर्वपद ‘त्रि’ संख्यावाची है।

पंचपात्रम् – पंचानां पात्राणां समाहारः।
पंचवटी – पंचानां वटानां समाहारः।
सप्तर्षिः – सप्तानां पषीणां समाहारः।
चतुर्युगम् – चतुर्णां युगानां समाहारः।

3. बहुव्रीहि – अन्यपदप्रधानः बहुब्रीहिः
इस समास में पूर्व तथा उत्तर पदों की प्रधानता न होकर किसी अन्य पद की प्रधानता होती है।
यथा
पीताम्बरः – पीतम् अम्बरम् यस्य सः (विष्णुः)।
यहा! न तो पीतम् शब्द की प्रधानता है और न अम्बरम् शब्द की अपितु पीताम्बरधारी किसी अन्य व्यक्ति (विष्णु) की प्रधानता है।
नीलकण्ठः – नीलः कण्ठः यस्य सः (शिवः)।
दशाननः – दश आननानि यस्य सः (रावण:)।
अनेककोटिसारः – अनेककोटिः सारः (धनम्) यस्य सः ।
विगलितसमृणिम् – विगलिता समृणिः यस्य तम् (पुरुषम्)।
प्रक्षालितपादम् – प्रक्षालितौ पादौ यस्य तम् (जनम्)।

4. द्वन्द्व – ‘उभयपदप्रधान: द्वन्द्वः’ इस समास में पूर्वपद और उत्तरपद दोनों को समान रूप से प्रधानता होती है। पदों के बीच में ‘च’ का प्रयोग विग्रह में होता है।
यथा
रामलक्ष्मणौ – रामश्च लक्ष्मणश्च।
पितरौ – माता च पिता च।
धर्मार्थकाममोक्षाः – धर्मश्च, अर्थश्च, कामरच, मोक्षश्च।
वसन्तग्रीष्मशिशिराः – वसन्तश्च ग्रीष्मश्च शिशिरश्च।

कविपरिचय – प्रो. हरिदत्त शर्मा इलाहाबाद केन्द्रीय विश्वविद्यालय में संस्कृत के आचार्य रहे हैं। इनके कई संस्कृत काव्य प्रकाशित हो चुके हैं। जैसे-गीतकंदलिका, त्रिपथगा, उत्कलिका, बालगीताली, आक्रन्दनम, लसल्लतिका इत्यादि। इनकी रचनाओं में समाज की विसंगतियों के प्रति आक्रोश तथा स्वस्थ वातावरण के प्रति दिशानिर्देश के भाव प्राप्त होते हैं।

Class 10 Sanskrit Shemushi Chapter 1 शुचिपर्यावरणम् Summary Translation in Hindi and English

पाठ परिचय – प्रस्तुत पाठ आधुनिक संस्कृत कवि हरिदत्त शर्मा के रचना संग्रह ‘लसल्लतिका’ से संकलित है। इसमें कवि ने महानगरों की यांत्रिक – बहुलता से बढ़ते प्रदूषण पर चिन्ता व्यक्त करते हुए कहा है कि यह लौहचक्र तन – मन का शोषक है, जिससे वायुमण्डल और भूमण्डल दोनों मलिन हो रहे हैं। कवि महानगरीय जीवन से दूर, नदी – निर्झर, वृक्षसमूह, लताकुञ्ज एवं पक्षियों से गुञ्जित वनप्रदेशों की ओर चलने की अभिलाषा व्यक्त करता है।
इस पाठ में कवि प्रत्येक मानव के स्वस्थ जीवन की कामना करता है। वह चाहता है कि सभी जगह साफ – सफाई हो एवं प्रदूषण मुक्त पृथ्वी हो।

1. दुर्वहमत्र जीवितं जातं प्रकृतिरेव शरणम्।
शुचि – पर्यावरणम्॥
महानगरमध्ये चलदनिशं कालायसचक्रम्।
मनः शोषयत् तनुः पेषयद् भ्रमति सदा वक्रम्॥
दुन्तिर्दशनैरमना स्यान्नैव जनग्रसनम्। शुचि…॥1॥

अन्वयः – अत्र जीवितं दुर्वहं जातम्, प्रकृति एव शरणम् शुचिपर्यावरणम्। महानगर – मध्ये कालायसचक्रम् अनिशं चलत मनः शोषयत. तनुः पेषयत् सदा वक्र भ्रमति। अमुना। दुर्दान्ते: दर्शनेः जनग्रसन न एवं स्यात।

शब्दार्थ: – दुर्वहम् – दुष्करम् (कठिन), जातम् – अभवत् (हो गया).शरणम् – आश्रयः (सहारा), अनिशम् – अहर्निशम् (दिन – रात), कालायसचक्रम् – लौहचक्रम् (लोहे का चक्र). शोषयत् – शुष्कीकुर्वत् (सुखाते हुए). तनुः – शरीरम् (शरीर), पेषयद् – पिष्टीकुर्वत् (पीसना करते हुए), वक्रम् – कुटिलम् (टेढा), दुर्दान्तैः – भयङ्करैः (भयानक), दशनैः – दन्तैः (दाँतों से). अमुना – अनेन (इससे), जननसनम् – जनभक्षणम् (मानव का विनाश) स्यात् – भवेत (हो)।

व्याख्या – यहाँ (महानगरों में) जीवन दूभर हो गया है। अब तो प्रकृति एवं स्वच्छे पर्यावरण ही एक मात्र सहारा (आश्रय) रह गया है। महानगर में दिन – रात चलता हुआ लोहे का पहिया मन को सूखाता हुआ, शरीर को पीसता हुआ हमेशा टेढा घूम रहा है। इसलिए इसके भयंकर दाँतो से लोगो का विनाश न हो जाए भाव यह है कि यदि महानगरो में जीवित रहना है तो पर्यावरण की शरण लेनी ही पड़ेगी।

2. कज्जलमलिनं धूमं मुञ्चति शतशकटीयानम्।
वाष्पयानमाला संधावति वितरन्ती ध्वानम्॥
यानानां पङ्क्तयो हनन्ताः कठिनं संसरणम्।
शुचि …112॥

अन्वयः – शतशकटीयां कज्जलमलिन घूमं मुञ्चति। वास्पयान माला ध्वान वितरन्ती संधावति अत्र यानाना अनन्ताः पक्तयः कठिन संसरणम्।।

शब्दार्थ: – कज्जलमलिनम् – कज्जलेन मलिनम् (काजल – सा मलिन (काला)). धूम: – अग्निवाहः (धुओं). मुञ्चति – त्यजति (छोड़ता है) शतशकटीयानम् – शकटीयानानां शतम् (सैकड़ों मोटर गाड़ियाँ), वाष्पयानमाला – वाष्पयानानां पंक्तिः (रेलगाड़ी की पंक्ति), वितरन्ती – ददती/वितरणं कुर्वाणा (देती हुई), ध्वानम् – ध्वनिम् (कोलाहल), संसरणम्सञ्चलनम् (चलना)।

व्याख्या – सैकड़ों मोटर कारें काजल जैसा गंदा धुआँ उगल रही है। रेलगाड़ी धुआँ छोड़ती हुई दौडती है। वाहनो की बहुत लम्बी – लम्बी कतारे है, चलना भी कठिन है अर्थात बहुत बड़ा जाम लगा रहता है।

3. वायुमण्डलं भृशं दूषितं न हि निर्मलं जलम्।
कुत्सितवस्तुमिश्रितं भक्ष्यं समलं धरातलम्॥
करणीय बहिरन्तर्जगति तु बहु शुद्धीकरणम्।
शुचि…॥3॥

अन्वयः – (महानगरेषु) वायुमण्डल भृशं दूषितम् निर्मल जलं (कत्राऽपि) न हि (विधते)। भक्ष्म कुल्सित वस्तु मिश्रितम्। धरातलं समल। अन्तः बहिः च जगति बहु शुद्धी करणं तु करणीयम्।।

शब्दार्थः – भृशम् – अत्यधिकम् (बहुत), निर्मलं – स्वच्छम् (स्वच्छ), कुत्सित वस्तु – कुवस्तु (मिलावटी पदार्थ). भक्ष्यम् – खाद्य पदार्थ (खाने योग्य), समलम् – मलेन् युक्तम् (मलसहितम्)।

व्याख्या – महानगरो में वायुमण्डल अधिक प्रदूषित है। जल भी साफ (स्वच्छ) नहीं है। खाद्य पदार्थों में भी मिलावट है। धरती गंदी हो गई हैं। संसार में आन्तरिक व बाह्य शुद्धि करना आवश्यक है। भाव यह है कि हमें साफ सफाई रखनी चाहिए।

4. कञ्चित् कालं नय मामस्मान्नगरान् बहुदूरम्।
प्रपश्यामि ग्रामान्ते निर्झर – नदी – पयःपूरम्।।
एकान्ते कान्तारे क्षणमपि मे स्यात् सञ्चरणम्।
शुचि…॥4॥

अन्वयः – कञ्चित कालं माम् अस्मात् नगरात बहु दूर नया नामान्ते निर्झर – पय नदी पूरं प्रपश्यामि। एकान्ते कान्वारे में क्षणम् अपि सञ्चरणं स्यात्।।

शब्दार्थः – नय – ले चलो (नामान्ते ग्रामस्य अन्ते (गाँव की सीमा पर), पयःपूरम – जलाशयम् (तालाब). कान्तारे – अरण्ये, वने (जंगल में), सञ्चरणम् – भ्रमणम् (घूमना)।

व्याख्या – कवि कहता है कि मुझे कुछ समय के लिए इस नगर से दूर ले चलो। गाँव की सीमा पर झरने नदी तथा तालाब को देखना चाहता हूँ एकान्त वन में मैं क्षण भर के लिए हो सही मेरा भ्रमण हो जाए।
भाव यह है कि महानगर से अच्छा ग्रामीण जीवन है ऐसा बताया गया है।

5. हरिततरूणां ललितलतानां माला रमणीया।
कुसुमावलिः समीरचालिता स्यान्मे वरणीया॥
नवमालिका रसालं मिलिता रुचिरं संगमनम्।
शुचि…॥5॥

अन्वयः – हरित – तरूणां ललित लतानां च रमणीया माला,समीर चालिता कुसुमुमावलि में वरणीया स्यात। नवमालिका रसालं मिलिता रूचिरं संगमनम् (स्यात)।

शब्दार्थ: – हरित – तरूणां (हरित वृक्षाणाम्), हरे पेड़ों का, कुसुमावलिः – कुसुम पंक्ति (फूलो की कतारे), समीर चालिता – पवन चालिता (हवा से चलाई गई), नवमालिका – मालती (चमेली), रसालम् – आम्रम् (आम) ,संगमनम् – मेलनं (समागम)।

व्याख्या – हरे भरे वृक्षों की, सुन्दर लताओं की माला तथा पवन द्वारा चलाई गई फूलों की पंक्तियाँ मेरे द्वारा वर्णन करने योग्य है। आम के वृक्ष से लगी चमेली का भी सुन्दर .समागम हो।

6. अयि चल बन्धो! खगकुलकलरव गुजितवनवेशम्।
पुर – कलरव सम्भ्रमितजनेभ्यो धृतसुखसन्देशम्।
चाकचिक्यजालं नो कुर्याज्जीवितरसहरणम्।
शुचि…॥6॥

अन्वयः – अपि बन्धो। खगकुल – कलख गुञ्चित – वनदेश चल। पुस्कल एव – सम्भ्रमित जनेभ्यः धृत – सुख संदेशम्। चाकचिक्य जालं जीवित रस – हरणं नो कुर्यात! ।

शब्दार्थ: – खगकुल कलख – पक्षि समूह की ध्वनि, पुरः कलख – नगरीय कालाहल चाकचिक्य – जालं – कृत्रिम प्रभाव पूर्ण जगत नो – न (नहीं)।

व्याख्या – हे बन्धु! पक्षि समूह के द्वारा गुञ्जायमान वन प्रदेश में चलो। महानगरो के शोरगुल के परेशान लोगों के लिए सुख का संदेश ग्रहण (धारण) करा चकाचोंध से युक्त इस दुनिया में जीवन के सुख का विनाश न कर।

7. प्रस्तरतले लतातरुगुल्मा नो भवन्तु पिष्टाः।
पाषाणी सभ्यता निसर्ग स्यान्न समाविष्टा॥
मानवाय जीवनं कामये नो जीवन्मरणम्।
शुचि…॥7॥

अन्वयः – लता – तरन – गुल्माः प्रस्तर तले पिष्टा: न भवन्त। निसर्गे पाषाणी सभ्यता, समाविष्टा न स्यात। मानवाय जीवन कामये जीवन मरणम् न कामये।

शब्दार्थः – लतातरूगुल्मा: – लताश्च, तखश्च, गुल्माश्च (लता वृक्ष और झाड़ी), पाषाणी – पर्वतमयी (पथरीली), निसर्ग प्रकृत्याम् – प्रकृति में, कामये – अभिलष्यामि (कामना करता है।)

व्याख्या – लताएँ, वृक्ष तथा झाड़ियों पत्थरों के नीचे न पिसे। प्रकृति में पंथरीली सभ्यता न समा जाए। मानव के जीवन की कामना करता हुँ। जीवित रहते हुए मैं मौत चाहता है।

These NCERT Solutions for Class 9 Science Chapter 4 Structure of the Atom Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Structure of the Atom NCERT Solutions for Class 9 Science Chapter 4

Class 9 Science Chapter 4 Structure of the Atom InText Questions and Answers

Question 1.
What are canal rays?
Answer:
Canal rays are positively charged radiations. These rays consist of positively charged particles known as protons. They were discovered by Goldstein in 1886.

Question 2.
If an atom contains one electron and one proton, will it cany any charge or not?
Answer:
An electron is a negatively charged; particle, whereas a proton is a positively charged; particle. The magnitude of their charges is equal. Therefore, an atom containing one electron and one proton will not carry any charge. Thus, it will be a neutral atom.

Question 3.
Name the three sub-atomic particles of an atom.
Answer:
The three sub-atomic particles of an atom are:

1. Protons
2. Electrons
3. Neutrons

Question 4.
Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?
Answer:
A helium atom has two neutrons. The mass of an atom is the sum of the masses of protons and neutrons present in its nucleus. Since helium atom has two protons, mass contributed by the two protons is (2 × 1) u = 2 u. Then, the remaining mass (4 – 2) u = 2 u is contributed \(\frac{2 \mathrm{u}}{1 \mathrm{u}}\) = 2 by neutrons.

Question 5.
Draw a sketch of Bohr’s model of an atom with three shells.
Answer:
Bohr’s model of an atom with three shells

Question 6.
What do you think would be the observation if the a-particle scattering experiment is carried out using a foil of a metal other than gold?
Answer:
If the a-scattering experiment is carried out using a foil of a metal rather than gold, there would be no change in the observation. In the a- scattering experiment, a gold foil was taken because gold is malleable and a thin foil of gold can be easily made. It is difficult to make such foils from other metals.

Question 7.
Write the distribution of electrons in carbon and sodium atoms?
Answer:
The total number of electrons in a carbon atom is 6. The distribution of electrons in carbon atom is given by:
First orbit or K-shell = 2 electrons
Second orbit or L-shell = 4 electrons
Or, we can write the distribution of electrons in a carbon atom as 2, 4.

The total number of electrons in a sodium atom is 11. The distribution of electrons in sodium atom is given by:
First orbit or K-shell = 2 electrons
Second orbit or L-shell = 8 electrons
Third orbit or M-shell = 1 electron
Or, we can write the distribution of electrons in a sodium atom as 2, 8, 1.

Question 8.
If K and L shells of an atom are full, then what would be the total number of electrons in the atom?
Answer:
The maximum number of electrons that can occupy K and L-shells of an atom are 2 and 8 respectively. Therefore, if K and L-shells of an atom are full, then the total number of electrons in the atom would be (2 + 8) = 10 electrons.

Question 9.
If number of electrons in an atom is 8 and number of protons is also 8, then (i) what is the atomic number of the atom and (ii) what is the charge on the atom?
Answer:
(i) The atomic number is equal to the number of protons. Therefore, the atomic number of the atom is 8.
(ii) Since the number of both electrons and protons is equal, therefore, the charge on the atom is 0.

Question 10.
With the help of Table 4.1, find out the mass number of oxygen and sulphur atom.
Answer:
Mass number of oxygen = Number of protons + Number of neutrons
= 8 + 8
= 16
Mass number of sulphur=Number of protons + Number of neutrons
= 16 + 16
= 32

Question 11.
For the symbol H, D and T tabulate three sub-atomic particles found in each of them.
Answer:

Question 12.
Write the electronic configuration of any one pair of isotopes and isobars.
Answer:
Two isoto of carbon are \(\frac {12}{6}\)C and \(\frac {14}{6}\)C.
The electronic configuration of \(\frac {12}{6}\)C is 2, 4.
The electronic configuration of \(\frac {14}{6}\)C is 2, 4.
[Isotopes have the same electronic configuration]
\(\frac {40}{20}\)Ca and \(\frac {40}{18}\)Ar are a pair of isobars
The electronic configuration of \(\frac {40}{20}\)Ca is 2, 8, 8, 2.
The electronic configuration of \(\frac {40}{18}\)Ar is 2, 8, 8.

Class 9 Science Chapter 4 Structure of the Atom Textbook Questions and Answers

Question 1.
Compare properties of electrons, protons and neutrons.
Answer:

Question 2.
What are the limitations of J.J. Thomson’s model of the atom?
Answer:
According to J.J. Thomson’s model of an atom, an atom consists of a positively charged sphere with electrons embedded in it. However, it was later found that the positively charged particles reside at the centre of the atom called the nucleus, and the electrons revolve around the nucleus.

Question 3.
What are the limitations of Rutherford’s model of the atom?
Answer:
According to Rutherford’s model of an atom, electrons revolve around the nucleus in fixed orbits. But, an electron revolving in circular orbits will not be stable because during revolution, it will experience acceleration. Due to acceleration, the electrons will lose energy in the form of radiation and fall into the nucleus. In such a case, the atom would be highly unstable and collapse.

Question 4.
Describe Bohr’s model of the atom.
Answer:
Bohr’s model of the atom:
Niels Bohr proposed the following postulates regarding the model of the atom.

1. Only certain orbits known as discrete orbits of electrons are allowed inside the atom.
2. While revolving in these discrete orbits, the electrons do not radiate energy.

These discrete orbits or shells are shown in the following diagram.

The first orbit (i.e., for n = 1) is represented by letter K. Similarly, for n = 2, it is L – shell, for n = 3, it is M – shell and for n = 4, it is N – shell. These orbits or shells are also called energy levels.

Question 5.
Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.
Answer:
The rules for writing of the distribution of electrons in various shells for the first eighteen elements are given below.
(i) The maximum number of electrons that a shell can accommodate is given by the formula ‘2n²‘, where ‘n’ is the orbit number or energy level index (n = 1, 2,3..).

The maximum number of electrons present in an orbit of n = 1 is given by 2n² = 2 × 12 = 2
Similarly, for second orbit, it is 2n² = 2 × 2² = 8
For third orbit, it is 2n² = 2 × 3² = 18
And so on ……
(ii) The outermost orbit can be accommodated by a maximum number of 8 electrons.
(iii) Shells are filled with electrons in a stepwise manner i.e., the outer shell is not occupied with electrons unless the inner shells are completely filled with electrons.

Question 6.
Define valency by taking examples of silicon and oxygen.
Answer:
The valency of an element is the combining capacity of that element. The valency of an element is determined by the number of valence electrons present in the atom of that element.

If the number of valence electrons of the atom of an element is less than or equal to four, then the valency of that element is equal to the number of valence electrons. For example, the atom of silicon has four valence electrons. Thus, the valency of silicon is four.

On the other hand, if the number of valence electrons of the atom of an element is greater than four, then the valency of that element is obtained by subtracting the number of valence electrons from eight. For example, the atom of oxygen has six valence electrons. Thus, tire valency of oxygen is(8 – 6) i.e., two.

Question 7.
Explain with examples (i) Atomic number (ii) Mass number (iii) Isotopes and (iv) Isobars. Give any two uses of isotopes.
Answer:
(i) Atomic number:
The atomic number of an element is the total number of protons present in the atom of that element. For example, nitrogen has 7 protons in its atom. Thus, the atomic number of nitrogen is 7.

(ii) Mass number:
The mass number of an element is the sum of the number of protons and neutrons present in the atom of that element. For example, tire atom of boron has 5 protons and 6 neutrons. So, the mass number of boron is 5 + 6 = 11.

(iii) Isotopes:
Isotopes are atoms of the same element having the same atomic number, but different mass numbers. For example, hydrogen has three isotopes. They are protium \(\left({ }_{1}^{1} \mathrm{H}\right)\), deuterium \(\left({ }_{1}^{2} \mathrm{H}\right)\), and tritium \(\left({ }_{1}^{3} \mathrm{H}\right)\).

(iv) Isobars:
Isobars are atoms having the same mass number, but different atomic numbers i.e., isobars are atoms of different elements having the same mass number. For example, \({ }_{20}^{40} \mathrm{Ca}\) and \({ }_{18}^{40} \mathrm{Ar}\) andare isobars.

Two uses of isotopes are:

1. One isotope of uranium is used as a fuel in nuclear reactors.
2. One isotope of cobalt is used in the treatment of cancer.

Question 8.
Na⁺ has completely filled K and L shells. Explain.
Answer:
An atom of Na has a total of 11 electrons. Its electronic configuration is 2,8,1. But, Na⁺ ion has one electron less than Na atom i.e., it has 10 electrons. Therefore, 2 electrons go to K-shell and 8 electrons go to L-shell, thereby completely filling K and L shells.

Question 9.
If bromine atom is available in tile form of, say, two isotopes \({ }_{35}^{79} \mathrm{Br}\) (49.7%) and \({ }_{35}^{81} \mathrm{Br}\) (50.3%), calculate the average atomic mass of bromine atom.
Answer:
It is given that two isotopes of bromine are \({ }_{35}^{79} \mathrm{Br}\)(49.7%) and \({ }_{35}^{81} \mathrm{Br}\) (50.3%). Then, the average atomic mass of bromine atom is given by:

= 80.006 u
= 80 u (approx)

Question 10.
The average atomic mass of a sample of an clement X is 16.2 u. What are the
percentages of isotopes \({ }_{8}^{16} \mathrm{X}\) and \({ }_{8}^{18} \mathrm{X}\) in the sample?
Answer:
It is given that the average atomic mass of the sample of element X is 16.2 u.
Let the percentage of isotope \({ }_{8}^{18} \mathrm{X}\) be y%. Thus,
the percentage of isotope \({ }_{8}^{16} \mathrm{X}\) will be (100 – y) %.

Therefore,

⇒ 18y + 1600 = 1620
⇒ 2y + 1600 = 1620
⇒ 2y +1620 – 1600
⇒ 2y = 20
⇒ y = 10
Therefore, the percentage of isotope \({ }_{8}^{18} \mathrm{X}\) is 10%.
And, the percentage of isotope \({ }_{8}^{16} \mathrm{X}\) is (100 – 10) % = 90%.

Question 11.
If Z = 3, what would be the valency of the element? Also, name the element
Answer:
By Z = 3, we mean that the atomic number of the element is 3. Its electronic configuration is 2, 1. Hence, the valency of the element is 1 (since the outermost shell has only one electron).

Therefore, the element with Z = 3 is lithium.

Question 12.
Composition of the nuclei of two atomic species X and Y are given as under

Give the mass numbers of X and Y. What is the relation between the two species?
Answer:
Mass number of X = Number of protons + Number of neutrons
= 6 + 6
= 12
Mass number of Y = Number of protons + Number of neutrons
= 6 + 8
= 14
These two atomic species X and Y have the same atomic number, but different mass numbers. Hence, they are isotopes.

Question 13.
For the following statements, write T for ‘True’ and F for ‘False’.
(a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons.
(b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.
(c) The mass of an electron is about \(\frac{1}{2000}\) times that of proton.
(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.
Answer:
(a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons: (F)
(b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral (F).
(c) The mass of an electron is about \(\frac{1}{2000}\) times that of proton. (T)
(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine. (F)

Question 14.
Put tick (√) against correct choice and cross (×) against wrong choice in the following question:
Rutherford’s alpha-particle scattering experiment was responsible for the discovery of
(a) Atomic nucleus
(b) Electron
(c) Proton
(d) Neutron
Answer:
Rutherford’s alpha-particle scattering experiment was responsible for the discovery of
(a) Atomic nucleus (√)
(b) Electron
(c) Proton
(d) Neutron

Question 15.
Put tick (√) against correct choice and cross (×) against wrong choice in the following question:
Isotopes of an element have
(a) the same physical properties
(b) different chemical properties
(c) different number of neutrons
(d) different atomic numbers
Answer:
Isotopes of an element have
(a) the same physical properties
(b) different chemical properties
(c) different number of neutrons (√)
(d) different atomic numbers

Question 16.
Put tick (√) against correct choice and cross (×) against wrong choice in the following question:
Number of valence electrons in Cl- ion are:
(a) 16
(b) 8
(c) 17
(d) 18
Answer:
Number of valence electrons in Cl- ion are:
(a) 16
(b) 8(√)
(c) 17
(d) 18

Question 17.
Which one of the following is a correct electronic configuration of sodium?
(a) 2, 8
(b) 8, 2, 1
(c) 2, 1, 8
(d) 2, 8, 1
Answer:
(d) The correct electronic configuration of sodium is 2, 8, 1.

Class 9 Science Chapter 4 Structure of the Atom Additional Important Questions and Answers

Very Short Answer Questions

Question 1.
What are nucleons?
Answer:
The subatomic particles present in the nucleus of an atom are called nucleons. These include protons and neutrons.

Question 2.
Which element does not contain any neutron?
Answer:
Hydrogen

Question 3.
Who discovered the presence of the protons in an atom?
Answer:
Goldstein after his discovery of anode rays.

Question 4.
What did Rutherford discover from his alpha particle scattering experiment?
Answer:
Rutherford from alpha particle scattering experiment had discovered the nucleus of an atom.

Question 5.
Which subatomic particles were not known when Rutherford performed his experiment?
Answer:
Neutrons

Question 6.
What is the number of protons and neutrons present in a helium atom?
Answer:
In a helium atom the number of both protons and neutrons is two.

Question 7.
What is common in isotopes of an element?
Answer:
Atomic number

Question 8.
What was the major drawback of Rutherford’s model of atom?
Answer:
Rutherford had failed to describe the stability of an atom.

Question 9.
What are the fundamental building blocks of matter?
Answer:
Atoms and molecules

Question 10.
What is the mass and charge of a proton?
Answer:
The mass of a .proton is taken as one unit and so also its charge is taken as one positive unit.

Question 11.
What is the charge on the nucleus of an atom?
Answer:
The nucleus of an atom is positively charged.

Question 12.
What are valence electrons?
Answer:
The electrons present in the outermost shell of an atom are called valence electrons.

Question 13.
If an atom has atomic number-16, what are the number of valence electrons and what is its valency?
Answer:
Electronic configuration: 2, 8, 6.
Valence electrons = 6
Valency = 2

Question 14.
Which isotope of uranium is used as nuclear fuel in nuclear reactor?
Answer:
U-235.

Short Answer Questions

Question 1.
How will you prove that matter is electrical in nature but neutral?
Answer:
When a glass rod rubbed with silk cloth is brought near an inflated balloon, the balloon gets attracted to the rod but when a glass rod without being rubbed to silk cloth is brought close to an inflated balloon nothing happens shows that matter is electrical in nature but neutral.

Question 2.
What made the scientists to realize that atom is divisible after Dalton proposed his theory of atom in which he described atom as indivisible?
Answer:
The attraction of bits of paper by a comb after combing dry hair or gluing of a balloon to a wall after rubbing made the scientists think that atom is divisble.

Question 3.
What is the charge and mass of an electron and a proton?
Answer:
Charge on an electron = -1.6 x 10^-19C
Mass of an electron = 1/1840 times of a proton
Charge on a proton = + 1.6 x 10^-19C
Mass of an electron = mass of a hydrogen atom

Question 4.
(i) What are the mass number (A) and atomic number (Z) of an element?
(ii) How are they indicated in a symbol of an atom?
Answer:
(i) Mass number refers to the sum of the numbers of protons and neutrons present in atom while the atomic number refers to the number of protons present in the nucleus of an atom.
(ii) Mass number is always written in superscript and atomic number in the subscript as shown below.

Question 5.
(i) What is the nucleus of atom?
(ii) What charge does the nucleus of an atom carry?
Answer:
(i) Nucleus is a small dense region present in the centre of an atom. It is 10s times smaller than an atom. It is like a football placed in the centre of football field, (ii) It contains positively charged protons and neutral neutrons, therefore it is positively charged.

Question 6.
What did Thomson propose about the model of an atom?
Answer:
Thomson proposed that:

• An atom consists of a positively charged into it.
• The negative and positive charges are equal in magnitude and hence, an atom is electrically neutral.

Question 7.
If in an element K shell is completely filled then what will be the
(a) number of valence electrons
(b) valence and
(c) name of element.
Answer:
(a) Number of valence electrons = 2
(b) Valence = Zero
(c) Name of element = Helium

Question 8.
If chlorine atom is available in the form of say two isotopes ³⁵C₁₇(75%). ³⁷Cl₁₇(25%). Calculate the average atomic mass of bromine.
Answer:
The average atomic mass of bromine would be

Question 9.
The average atomic mass of a sample of an element X is 12.2 u. What is the percentage of isotopes ¹²X₆ and ¹⁴X₆ in the sample?
Answer:
Atomic mass of X =12 unit
Let the percentage of ¹²X₆ = X %
Percentage of ¹⁴X₆ = Y% = (100 – x)%

Question 10.
What are isotopes? State their uses.
Answer:
Isotopes of an element are the atoms which have the same atomic number: different atomic mass number because of the presence of the different number neutrons. These isotopes are used in

• Generation of electricity as fuels in nuclear power stations such as uranium-235.
• In chemotherapy such as Co-60 is used in treatment of cancer.
• Isotope of iodine is used in treatment of goitre.
• Research works to find the metabolic pathways.

Question 11.
How is an isotope different from an isobar?
Answer:
Isotopes are the atoms of an element which have same atomic number – differ in the atomic mass number because they carry different number of neutrons but Isobars are the atoms of different elements which have same atomic mass number but they differ in their atomic number.

Question 12.
Which of the following are the isotopes and isobars? Why?
¹⁸X₈, ¹⁸Y₆, ¹⁶X₈
Answer:
¹⁸X₈, and ¹⁸Y₆ are isobars because they have different atomic number but same atomic mass number.
¹⁸X₈, and ¹⁶X₈ are isotopes because they have same atomic number but different atomic masses.

Question 13.
How is an alpha particle different from an atom of helium?
Answer:
Alpha particle is the nucleus of helium represented by the formula without any electron but an atom of helium consists of 2 electrons along nucleus having two protons and neutrons.

Question 14.
Calculate the number of electrons, protons and neutrons in the following
⁴⁰X₂₀, ¹⁴Y₆, ²³⁸Z₉₂
Answer:
⁴⁰X₂₀ – Number of protons = 20, Number of electrons = 20 Number of neutrons = 20
¹⁴Y₆ – Number of protons = 6, Number of electrons = 6 Number of neutrons = 8
²³⁸Z₉₂ – Number of protons = 92, Number of electrons = 92 Number of neutrons = 146

Question 15.
Why the valence electrons are considered responsible for the chemical activity of an element?
Answer:
Valence electrons are the electrons present in the outermost shell of an atom. The number of these electrons determines that how many electrons an atom need to gain or lose, to gain stability. The lesser is the number of electrons required to be lost or gained, the reactive is the element.

Question 16.
How is a discharge tube different from an ordinary tube?
Answer:
A discharge is a tube with the gas under very low pressure i.e. 1 atmospheric pressure where it is possible to generate the electric discharge but in an ordinary tube has average atmospheric pressure in which an electrical discharge cannot be produced in any condition.

Long Answer Questions

Question 1.
What are cathode rays? How are they produced?
Answer:
When an electric discharge is produced in a discharge tube at low pressure 10^-2 atmospheric pressure and the voltage of 10,000 V, the rays emitted from the cathode are called cathode rays. These rays consist of negatively charge particles called electrons because they get deflected towards the positively charged electrode when passing through an electric field.

In discharge tube, the low pressure is maintained to have less number of molecules hence, minimum interference in the path of the cathode rays emitted from cathode. The emission of these rays proved that the atoms are not indivisible as stated by Dalton in his atomic theory but contain negatively charge electrons.

Question 2.
What are anode rays? Describe their nature.
Answer:
Anode rays are the positively charged rays produced in a discharge tube having a perforated cathode. These rays consist of positively charge particles called protons. These rays get deflected towards the negatively charged electrode when passing through an electric field.

The charge on a proton is equal to the charge on an electron, 1.6 × 10^-19C but is resite in sign being positively charged.

Question 3.
What observations did Rutherford made in his alpha particles scattering experiment? What did he conclude from his observations?
Answer:
Rutherford in his alpha particle experiment when he made the alpha particles incident on the surface of a very thin and fine gold foil observed that

• Most of the fast moving alpha particles passed through the gold foil.
• Some of the alpha particles underwent deflection in their path.

• Very few i.e. one out of 12,000 alpha particle bounced back at 180°.
  From his observations Rutherford concluded and proposed that
• There is a positively charged centre in an atom. He called this positively charged centre as nucleus.
• The size of the nucleus is very small as compared to the size of an atom.
• The negatively charged electrons are present outside the nucleus revolving around it.

Question 4.
Explain Rutherford’s α-particle scattering experiment and give its observation and conclusion drawn.
Answer:
Rutherford’s α-particle scattering experiment:
Fast moving α-particles were made to fall on a thin gold foil. Particles have + 2 charge and 4u mass, and considerable amount of energy.

Observations:

• Most of the α-particles passed straight through the foil.
• Some Of the α-particles were deflected by small angles by the foil.
• One out of every 12000 particles rebounded.

Conclusion from observation:

• Most of the space inside the foil is empty.
• Positive charge of atom occupies very less space.
• Mass of the atom is concentrated in the centre with all positive charge concentrated in small volume within the atom.