Carbon – Introduction | Class 10 Science

🧪 Carbon — Introduction

Class 10 Science | Carbon and Its Compounds | CBSE + Foundation + Competitive

🧪 Carbon — Introduction / कार्बन का परिचय

📘 1. Introduction to Carbon / कार्बन का परिचय

English: Carbon is a non-metallic element with atomic number 6. It is represented by the symbol C. Carbon is present in living organisms, fuels, food, medicines, plastics and many other substances.

हिन्दी: कार्बन एक अधातु तत्व है जिसका परमाणु क्रमांक 6 है। इसका प्रतीक C है। कार्बन जीवित जीवों, ईंधनों, भोजन, औषधियों, प्लास्टिक तथा अनेक अन्य पदार्थों में पाया जाता है।

Atomic Number of Carbon = 6
Electronic Configuration = 2, 4
Valency = 4

🌐 2. Why Does Carbon Form a Large Number of Compounds?

Carbon forms a very large number of compounds mainly because of two important properties:

1. Catenation / श्रृंखलन
Carbon atoms can bond with one another to form long chains, branched chains and rings.

2. Tetravalency / चतुसंयोजकता
Carbon has four valence electrons and can form four covalent bonds with other atoms.

Key Concept:

Catenation + Tetravalency → Enormous number of carbon compounds

श्रृंखलन + चतुसंयोजकता → कार्बन यौगिकों की बहुत बड़ी संख्या

🔗 3. What is Catenation? / श्रृंखलन क्या है?

Catenation is the ability of an element to form covalent bonds with atoms of the same element, thereby forming chains, branches and rings.

श्रृंखलन किसी तत्व के परमाणुओं की अपने ही समान तत्व के परमाणुओं के साथ सहसंयोजक बंध बनाने की क्षमता है, जिससे श्रृंखला, शाखित श्रृंखला और वलय बन सकते हैं।

C — C — C — C — C
Straight carbon chain / सीधी कार्बन श्रृंखला

   C
   |
C — C — C
   |
   C
Branched carbon structure / शाखित संरचना

Carbon shows extensive catenation because the C–C bond is strong and stable.

कार्बन में व्यापक श्रृंखलन का प्रमुख कारण यह है कि C–C बंध मजबूत और स्थिर होता है।

4️⃣ 4. What is Tetravalency of Carbon? / कार्बन की चतुसंयोजकता क्या है?

Carbon has atomic number 6 and electronic configuration 2,4. Therefore, it has four electrons in its outermost shell.

कार्बन का परमाणु क्रमांक 6 और इलेक्ट्रॉनिक विन्यास 2,4 है। इसलिए इसकी बाहरी कक्षा में चार इलेक्ट्रॉन होते हैं।

Carbon generally forms four covalent bonds to achieve a stable electronic configuration.

स्थिर इलेक्ट्रॉनिक विन्यास प्राप्त करने के लिए कार्बन सामान्यतः चार सहसंयोजक बंध बनाता है।

    H
    |
H — C — H
    |
    H
Methane (CH₄) / मीथेन

Exam Point:
The valency of carbon is 4, so carbon is called a tetravalent element.

परीक्षा बिंदु:
कार्बन की संयोजकता 4 होती है, इसलिए इसे चतुसंयोजी तत्व कहते हैं।

🤝 5. Why Does Carbon Form Covalent Bonds?

Carbon has four valence electrons. It would require four more electrons to complete its outer shell, but losing or gaining four electrons is energetically difficult.

कार्बन की बाहरी कक्षा में चार इलेक्ट्रॉन होते हैं। बाहरी कक्षा को पूर्ण करने के लिए इसे चार और इलेक्ट्रॉनों की आवश्यकता होती है, लेकिन चार इलेक्ट्रॉन खोना या प्राप्त करना ऊर्जात्मक रूप से कठिन होता है।

Therefore, carbon generally achieves stability by sharing electrons with other atoms.

इसलिए कार्बन सामान्यतः अन्य परमाणुओं के साथ इलेक्ट्रॉनों की साझेदारी करके स्थिरता प्राप्त करता है।

The shared electrons form covalent bonds.

इलेक्ट्रॉनों की यह साझेदारी सहसंयोजक बंध बनाती है।

🧬 6. Covalent Bond Formation in Methane / मीथेन में सहसंयोजक बंध

Methane has the formula CH₄. One carbon atom shares electrons with four hydrogen atoms.

मीथेन का सूत्र CH₄ है। इसमें एक कार्बन परमाणु चार हाइड्रोजन परमाणुओं के साथ इलेक्ट्रॉनों की साझेदारी करता है।

CH₄ = Carbon + 4 Hydrogen atoms

Each C–H bond is formed by sharing one pair of electrons between carbon and hydrogen.

प्रत्येक C–H बंध कार्बन और हाइड्रोजन के बीच इलेक्ट्रॉनों की एक जोड़ी की साझेदारी से बनता है।

⚛️ 7. Electron Sharing in Carbon / कार्बन में इलेक्ट्रॉन साझेदारी

Concept / अवधारणा	Explanation / व्याख्या
Valence electrons	Carbon has 4 valence electrons.
Required for octet	Carbon needs 4 more electrons to complete its octet.
Loss of electrons	Loss of four electrons requires very high energy.
Gain of electrons	Gain of four electrons is also energetically unfavourable.
Solution	Carbon shares electrons and forms covalent bonds.

🔬 8. General Features of Carbon Covalent Compounds

• They generally have strong covalent bonds within molecules.
• They generally have relatively low melting and boiling points compared with ionic compounds.
• They are generally poor conductors of electricity because they do not have free ions.
• Many carbon compounds are molecular in nature.

🔗 9. Types of Covalent Bonds in Carbon Compounds

Bond	Shared Electron Pairs	Example
Single bond	1 pair	Ethane (C₂H₆)
Double bond	2 pairs	Ethene (C₂H₄)
Triple bond	3 pairs	Ethyne (C₂H₂)

🔗 10. Strength of Carbon–Carbon Bond / कार्बन-कार्बन बंध

The carbon atom is relatively small, so the nucleus of one carbon atom can form a strong covalent bond with another carbon atom.

कार्बन परमाणु का आकार अपेक्षाकृत छोटा होता है, इसलिए एक कार्बन परमाणु का नाभिक दूसरे कार्बन परमाणु के साथ मजबूत सहसंयोजक बंध बना सकता है।

This strong C–C bonding is an important reason for extensive catenation.

यह मजबूत C–C बंध व्यापक श्रृंखलन का एक महत्वपूर्ण कारण है।

📊 11. Catenation vs Tetravalency

Catenation / श्रृंखलन	Tetravalency / चतुसंयोजकता
Ability to bond with other carbon atoms.	Ability to form four covalent bonds.
Produces chains, branches and rings.	Allows carbon to bond with H, O, N, halogens and other atoms.
Responsible for carbon skeleton formation.	Responsible for many possible bonding arrangements.

🌐 12. Why Carbon Compounds Are So Numerous

The huge variety of carbon compounds arises because carbon can:

1. Bond with other carbon atoms.
2. Form long chains.
3. Form branched chains.
4. Form cyclic structures.
5. Form single, double and triple bonds.
6. Bond with hydrogen, oxygen, nitrogen, sulphur and halogens.

📝 13. 30 MCQs – Carbon Introduction

Q1 What is the atomic number of carbon? / कार्बन का परमाणु क्रमांक क्या है?

A. 4

B. 6

C. 8

D. 12

Answer: B — Carbon has atomic number 6.

Q2 What is the electronic configuration of carbon?

A. 2,4

B. 2,6

C. 4,2

D. 2,8

Answer: A — Carbon has 6 electrons: 2 in K-shell and 4 in L-shell.

Q3 What is the valency of carbon?

A. 1

B. 2

C. 3

D. 4

Answer: D — Carbon is tetravalent.

Q4 What is catenation?

A. Bonding of carbon with metals only

B. Bonding of atoms of the same element to form chains or rings

C. Loss of all electrons

D. Formation of ions only

Answer: B.

Q5 Why does carbon form a large number of compounds?

A. Due to catenation and tetravalency

B. Due to radioactivity

C. Due to metallic nature

D. Due to its high density

Answer: A.

Q6 Carbon generally forms which type of bonds?

A. Ionic bonds only

B. Covalent bonds

C. Metallic bonds only

D. Hydrogen bonds only

Answer: B.

Q7 How many valence electrons does carbon have?

A. 2

B. 3

C. 4

D. 6

Answer: C.

Q8 Carbon forms covalent bonds mainly by:

A. Sharing electrons

B. Losing all protons

C. Gaining neutrons

D. Losing its nucleus

Answer: A.

Q9 Which molecule demonstrates tetravalency of carbon?

A. H₂

B. CH₄

C. O₂

D. N₂

Answer: B — Methane demonstrates four C–H bonds.

Q10 The ability of carbon to form bonds with itself is called:

A. Ionisation

B. Catenation

C. Reduction

D. Oxidation

Answer: B.

Q11 Carbon can form:

A. Only straight chains

B. Only rings

C. Chains, branches and rings

D. Only ionic lattices

Answer: C.

Q12 Which bond is formed by sharing one pair of electrons?

A. Single covalent bond

B. Double covalent bond

C. Triple covalent bond

D. Ionic bond

Answer: A.

Q13 A double covalent bond involves sharing of:

A. One electron

B. One pair of electrons

C. Two pairs of electrons

D. Four pairs of electrons

Answer: C.

Q14 A triple bond involves sharing of:

A. One pair

B. Two pairs

C. Three pairs

D. Four pairs

Answer: C.

Q15 Which is an example of a molecule containing a double bond between carbon atoms?

A. Ethane

B. Ethene

C. Methane

D. Propane

Answer: B — Ethene contains C=C.

Q16 Which compound contains a carbon-carbon triple bond?

A. Ethane

B. Ethene

C. Ethyne

D. Methane

Answer: C — Ethyne contains C≡C.

Q17 Why is C–C bonding important in carbon chemistry?

A. It enables formation of carbon chains

B. It prevents all compounds

C. It makes carbon radioactive

D. It removes valence electrons

Answer: A.

Q18 Carbon has how many electrons in its outermost shell?

A. 1

B. 2

C. 4

D. 8

Answer: C.

Q19 Why does carbon not normally form C⁴⁺ easily?

A. Removing four electrons requires very high energy

B. Carbon has no electrons

C. Carbon is a noble gas

D. Carbon has eight valence electrons

Answer: A.

Q20 Why does carbon not normally form C⁴⁻ easily?

A. Gaining four electrons is energetically unfavourable

B. Carbon has no nucleus

C. Carbon is a metal

D. Carbon has zero valency

Answer: A.

Q21 The stable bonding strategy of carbon is mainly:

A. Electron sharing

B. Complete electron loss

C. Complete electron gain

D. Proton sharing

Answer: A.

Q22 Which of the following is NOT a major reason for the huge number of carbon compounds?

A. Catenation

B. Tetravalency

C. Ability to form multiple bonds

D. Very high atomic mass

Answer: D.

Q23 Carbon can form covalent bonds with:

A. Hydrogen

B. Oxygen

C. Nitrogen

D. All of these

Answer: D.

Q24 Which property allows carbon to form branched chains?

A. Catenation

B. Magnetism

C. Radioactivity

D. Metallic lustre

Answer: A.

Q25 Which statement about carbon is correct?

A. It has four valence electrons

B. It has one valence electron

C. It is a noble gas

D. It normally forms only ionic compounds

Answer: A.

Q26 Which is an important consequence of tetravalency?

A. Carbon can form many different structures

B. Carbon cannot bond with hydrogen

C. Carbon forms only salts

D. Carbon has no chemical activity

Answer: A.

Q27 Which of the following contains a carbon-carbon single bond?

A. Ethane

B. Ethene

C. Ethyne

D. Carbon dioxide

Answer: A.

Q28 The term tetravalency means carbon can generally form:

A. One covalent bond

B. Two covalent bonds

C. Three covalent bonds

D. Four covalent bonds

Answer: D.

Q29 Which feature is responsible for the stability of carbon chains?

A. Strong C–C bonds

B. Weak C–C bonds

C. Metallic bonding

D. Ionic bonding only

Answer: A.

Q30 Carbon chemistry is exceptionally diverse because carbon can:

A. Only form C–C single bonds

B. Form chains, branches, rings and multiple bonds

C. Only form ionic compounds

D. Only form compounds with oxygen

Answer: B.

✍️ 14. 30 Subjective Questions with Answers

1 Mark Q1. What is the atomic number of carbon?

Answer: 6.
हिन्दी: कार्बन का परमाणु क्रमांक 6 है।

1 Mark Q2. What is the valency of carbon?

Answer: 4.

1 Mark Q3. What is catenation?

Answer: The ability of carbon atoms to form covalent bonds with other carbon atoms is called catenation.

1 Mark Q4. How many valence electrons does carbon have?

Answer: Four.

1 Mark Q5. Name the type of bond generally formed by carbon.

Answer: Covalent bond.

2 Marks Q6. Why does carbon form a large number of compounds?

Answer: Carbon forms a large number of compounds mainly because of its catenation and tetravalency.

2 Marks Q7. What is tetravalency of carbon?

Answer: Carbon has four valence electrons and generally forms four covalent bonds. This property is called tetravalency.

2 Marks Q8. Why does carbon form covalent bonds?

Answer: Carbon has four valence electrons. Losing or gaining four electrons is energetically difficult, so carbon achieves stability mainly by sharing electrons and forming covalent bonds.

2 Marks Q9. Why is catenation important in carbon chemistry?

Answer: Catenation allows carbon atoms to form long chains, branched chains and rings, producing a very large variety of compounds.

2 Marks Q10. Write the electronic configuration of carbon.

Answer: Carbon has atomic number 6, so its electronic configuration is 2,4.

3 Marks Q11. Explain catenation with an example.

Answer: Catenation is the ability of carbon to form covalent bonds with other carbon atoms. It allows formation of chains, branches and rings. For example:

C–C–C–C

represents a carbon chain.

3 Marks Q12. Explain tetravalency of carbon.

Answer: Carbon has four electrons in its outermost shell. It shares electrons with other atoms and can generally form four covalent bonds. Therefore, carbon is called tetravalent.

3 Marks Q13. Why can carbon not easily form C⁴⁺ or C⁴⁻ ions?

Answer: Removing four electrons from carbon requires very high energy, while gaining four electrons is also energetically unfavourable. Hence carbon generally shares electrons instead of forming C⁴⁺ or C⁴⁻ ions.

3 Marks Q14. Explain why carbon forms covalent bonds.

Answer: Carbon has four valence electrons. It needs four more electrons for an octet, but complete transfer of four electrons is difficult. Therefore, it shares electrons with other atoms and forms covalent bonds.

3 Marks Q15. State three reasons for the large number of carbon compounds.

Answer:
1. Catenation.
2. Tetravalency.
3. Ability to form single, double and triple bonds.

4 Marks Q16. Explain the role of catenation in the formation of carbon compounds.

Answer: Carbon atoms form strong C–C covalent bonds. As a result, they can link with one another to form long chains, branched chains and rings. This enormous structural variety contributes greatly to the large number of carbon compounds.

4 Marks Q17. Explain the role of tetravalency in carbon chemistry.

Answer: Carbon can form four covalent bonds. These bonds can be formed with carbon as well as hydrogen, oxygen, nitrogen, sulphur and halogens. This allows many different molecular structures and compounds to exist.

4 Marks Q18. Differentiate between catenation and tetravalency.

Catenation	Tetravalency
Ability to bond with atoms of the same element.	Ability to form four covalent bonds.
Helps form chains, branches and rings.	Allows bonding with many different atoms.
Produces carbon skeletons.	Produces different bonding arrangements.

4 Marks Q19. Explain the formation of methane using covalent bonding.

Answer: Carbon has four valence electrons and each hydrogen has one valence electron. Carbon shares one electron with each of four hydrogen atoms. Thus, four C–H covalent bonds are formed and carbon achieves an octet.

Formula: CH₄

4 Marks Q20. Explain why carbon-carbon bonds are important.

Answer: C–C bonds are strong and stable. They allow carbon atoms to join together into long chains, branched structures and rings. This property is responsible for the enormous diversity of carbon compounds.

5 Marks Q21. Why does carbon form a large number of compounds? Explain in detail.

Answer:
Carbon forms a very large number of compounds because:
1. It shows extensive catenation.
2. It is tetravalent.
3. It forms strong C–C bonds.
4. It can form single, double and triple bonds.
5. It can combine with many elements such as H, O, N, S and halogens.

5 Marks Q22. Explain catenation and its importance.

Answer: Catenation is the ability of carbon atoms to form covalent bonds with one another. Because C–C bonds are strong, carbon can form long straight chains, branched chains and cyclic structures. Catenation is one of the main reasons for the large variety of carbon compounds.

5 Marks Q23. Explain tetravalency of carbon with reference to its electronic configuration.

Answer: Carbon has atomic number 6 and electronic configuration 2,4. It therefore has four valence electrons. Instead of completely losing or gaining four electrons, carbon generally shares electrons with other atoms. It can form four covalent bonds and is therefore called tetravalent.

5 Marks Q24. Why does carbon form covalent compounds instead of ionic compounds in most cases?

Answer: Carbon has four valence electrons. Losing four electrons requires very high energy, while gaining four electrons is also not favourable. Hence carbon achieves stability by sharing electrons with other atoms, resulting in covalent compounds.

5 Marks Q25. Explain how carbon can form different types of bonds.

Answer: Carbon can share one, two or three pairs of electrons between atoms. Thus it can form:

1. Single bond → one shared pair.
2. Double bond → two shared pairs.
3. Triple bond → three shared pairs.

Examples are ethane, ethene and ethyne respectively.

6 Marks Q26. Explain the four important reasons for the versatility of carbon.

Answer:
1. Tetravalency: Carbon can form four covalent bonds.

2. Catenation: Carbon atoms form strong C–C bonds.

3. Multiple bonding: Carbon can form single, double and triple bonds.

4. Combination with many elements: Carbon bonds with H, O, N, S and halogens, producing many different compounds.

6 Marks Q27. Explain why carbon does not normally form C⁴⁺ and C⁴⁻ ions.

Answer:
Carbon has four valence electrons.

Formation of C⁴⁺: Carbon would have to lose four electrons. This requires an extremely large amount of energy.

Formation of C⁴⁻: Carbon would have to gain four electrons. This is also energetically unfavourable because of electron-electron repulsion and the difficulty of accommodating four additional electrons.

Therefore, carbon generally shares electrons and forms covalent bonds.

6 Marks Q28. Describe the electronic basis of covalent bonding in carbon.

Answer:
Carbon has atomic number 6 and electronic configuration 2,4. It has four valence electrons and requires four more electrons to complete its octet. Complete transfer of four electrons is not energetically favourable. Therefore carbon shares electrons with other atoms. Shared electron pairs form covalent bonds, allowing carbon to achieve a stable outer-shell configuration.

6 Marks Q29. Explain how catenation and tetravalency together make carbon chemistry highly diverse.

Answer:
Catenation allows carbon atoms to join with one another and form long chains, branched chains and rings. Tetravalency allows each carbon atom to form four covalent bonds with carbon and other elements. Together, these properties permit a huge variety of molecular structures. Carbon can also form single, double and triple bonds, further increasing the diversity.

6 Marks Q30. “Carbon is a versatile element.” Justify the statement.

Answer:
Carbon is called versatile because:
1. It has tetravalency.
2. It shows extensive catenation.
3. It forms strong C–C bonds.
4. It forms straight and branched chains.
5. It forms cyclic structures.
6. It forms single, double and triple covalent bonds.
7. It combines with many elements to produce an enormous variety of compounds.

🚀 15. Quick Revision / त्वरित पुनरावृत्ति

Carbon Symbol → C

Atomic Number → 6

Electronic Configuration → 2,4

Valence Electrons → 4

Valency → 4

Catenation → Carbon atoms bond with one another to form chains, branches and rings.

Tetravalency → Carbon can form four covalent bonds.

Covalent Bond → Bond formed by sharing of electrons.

Single Bond → 1 shared electron pair

Double Bond → 2 shared electron pairs

Triple Bond → 3 shared electron pairs

🎯 CBSE Exam Tip:

सबसे महत्वपूर्ण चार बातें याद रखें:

1. Carbon has 4 valence electrons.
2. Carbon is tetravalent.
3. Carbon shows catenation.
4. Carbon mainly forms covalent bonds by sharing electrons.

Key Formula:
Catenation + Tetravalency + Multiple Bonding = Huge Diversity of Carbon Compounds