Carbon and Its Allotropes – at a glance

 

Carbon is found in Group IV, Period II of the periodic table. Its electronic configuration is 1s² 2s² 2p². It occurs naturally in different forms called allotropes.

Allotropy

Allotropy is the ability of an element to exist in two or more different forms but in the same physical state.

I. Crystalline allotropes: Diamond, Graphite, Fullerenes

Ii. Amorphous forms: Coal, Charcoal, Coke, Soot, lampblack 

Uses: cutting tools, drilling, jewelry, precision instruments.

Crystalline Allotropes of carbon 

1. Diamond

Each carbon atom is bonded to 4 other carbon atoms in a tetrahedral structure. Making diamond a giant molecule with an octahedral shape (Forms a rigid 3D network.)

Properties of diamond 

i. It is the Hardest natural substance known 

ii. High melting point

iii. It is resistant to chemical attack.

iv.. It does not conduct electricity 

v. It is Transparent and shiny ( it has a high refractive index)

Uses:

I. It is used for making Cutting tools

II. It is used as Jewelry

III. It is used for making Industrial drilling machines 

2. Graphite

Graphite has flat layers of carbon atoms with free electrons. Each carbon atom in graphite bonds with 3 others forming hexagonal layers.

Each Layers are weakly held together by weak van der walls forces of attraction which makes it easy for one layer to easily slide over another (causing graphite to flake easily) hence graphite is used as s a lubricant.

Properties of graphite 

i. Soft and slippery

ii. Good Conductors of electricity (due to free electrons)

iii. It is Black and opaque

iv. It has a high melting point

Uses:

i. It is used in making lead Pencil 

ii. It is used as a dry Lubricants

iii. It is used as Electrodes in batteries

iv. It is used for lining the inside of crucibles 

3.  Fullerenes (Modern Allotrope)

Fullerenes (e.g. C₆₀) are spherical shape (like a football) carbon molecules called buckyballs (Buckminsterfullerene) (C₆₀) or C₇₀ and others – elongated shapes

 The carbon atoms are arranged in closed hollow structures such as spheres, ellipsoids, or tubes.

Structure

 i. Carbon atoms are arranged in hexagons and pentagons

ii. The most common fullerene is Buckminsterfullerene (C₆₀), which has a spherical shape like a football

iii. Each carbon atom forms three covalent bonds (sp² hybridization)

Properties

I. They have light weight but are very strong.

ii. They have Good electrical conductivity

iii. They have High stability and 

iv. They can act as antioxidants

Uses

i.  Nanotechnology and electronics      

ii. Drug delivery in medicine

iii. They are used as Lubricants

iv. They are used as Superconductors (in some modified forms)

Carbon Nanotubes   (cylindrical fullerenes)

Cylindrical tubes made of graphene

Properties 

i. They are Very strong

ii. The have Good electrical conductivity

Uses:

I. They are used in Nanotechnology

II. Used in Medicine (for drug delivery)

III. Used in making Electronics

Graphene

Structure: This is a single layer of graphite (one atom thick)

Properties of graphene 

i. It is Extremely strong

ii. It is an Excellent conductor of heat and electricity

iii. It is Flexible and lightweight

Uses:

i. It is used in Electronics

ii. It is used in Sensors

iii. It is used in Advanced materials

 Amorphous Carbon

i. Charcoal – 

a. Wood charcoal  ( absorbs 

b.  sugar charcoal

c. animal charcoal 

Uses 

i. absorbs gases and colours

ii. as fuel 

ii. Carbon black & lampblack – used in tyres, inks and polish

iii. Coal – used mainly as fuel

 Types of Coal (check post on coal): there are four stages of coal

• Peat – about 60% carbon
• Lignite – about 67% carbon
• Bituminous – about 88% carbon
• Anthracite – about 94% carbon (hardest and purest)

 Destructive Distillation of Coal:-

This is when coal is heated to a very high temperature in the absence of air. 

The products got are 

Coal → Coal gas + Coal tar + Ammoniacal liquor + Coke 

Gasification of coke:   when coke is heated to red hot and white hot and air and steam blown over it, it produces two types of gases (fuel gases)

 i. Producer gas: produced when air is blown over white hot coke      C_(s) → CO + N₂

ii.Water gas: Produce when steam is blown over red-hot coke           C(s) →    CO + H₂

iii. Synthetic gas – CO + H₂

Why Carbon Forms Many Allotropes

Carbon’s ability to form many allotropes is due to:

i. Catenation (bonding with itself)

ii. Ability to form different bond types (single, double)

iii. Flexibility in bonding arrangements

 Chemical Properties of Carbon

i.  Carbon burns in oxygen to form CO₂ or CO

  C_(s) + O_2(s) → CO_(g)  (limited oxygen)

   C_(s) + O_{2(s),/sub. → CO2(s)   (excess oxygen)}  

ii. Combines with elements like sulphur and hydrogen

 

C_(s) + S_(s) → CS₂

C_(s) + H_{2(g) →}   CH₄

iii. Acts as a reducing agent in metal extraction

 iv. Fe₂O₃ + C_{(s) →}  Fe_(s) + CO_2(g)

Is oxidized by strong acids to form CO₂

2H₂SO_4(aq) + C(s) → 2SO_2(g) + 2H₂O_(g) + CO_2(s)

Objective Questions (Carbon & Its Allotropes)

1. Carbon belongs to which group in the periodic table?
   A. Group I
   B. Group II
   C. Group IV
   D. Group VI

2. The atomic number of carbon is:
   A. 4
   B. 6
   C. 12
   D. 14

3. The ability of carbon to form long chains is called:
   A. Isomerism
   B. Catenation
   C. Polymerization
   D. Hybridization

4. Which of the following is an amorphous form of carbon?
   A. Diamond
   B. Graphite
   C. Charcoal
   D. Fullerene

5. Diamond is hard because:
   A. It contains free electrons
   B. It has strong covalent bonds in a 3D network
   C. It is metallic
   D. It contains impurities

6. Which allotrope of carbon conducts electricity?
   A. Diamond
   B. Graphite
   C. Charcoal
   D. Coke

7. In graphite, each carbon atom is bonded to how many other carbon atoms?
   A. 2
   B. 3
   C. 4
   D. 6

8. The structure of diamond is:
   A. Layered
   B. Planar
   C. Octahedral 

9. 
   D. Linear

10. Which allotrope of carbon is used as a lubricant?
    A. Diamond
    B. Graphite
    C. Coal
    D. Coke

11. The black soot obtained from incomplete combustion is called:
    A. Coke
    B. Charcoal
    66C. Lampblack
    D. Coal tar

12. 0Which allotrope of carbon is the hardest natural substance?
    A. Graphite
    B. Diamond
    C. Coke
    D. Charcoal

13. Fullerenes are composed of carbon atoms arranged in:
    A. Chains
    B. Sheets
    C. Spherical shapes
    D. Cubes

14. Which of the following is NOT an allotrope of carbon?
    A. Graphene
    B. Diamond
    C. Silicon
    D. Fullerene

15. The valency of carbon is:
    A. 2
    B. 3
    C. 4
    D. 6

16. Coal is mainly composed of:
    A. Hydrogen
    B. Oxygen
    C. Carbon
    D. Nitrogen

17. Which allotrope has a layered structure with weak forces between layers?
    A. Diamond
    B. Graphite
    C. Fullerene
    D. Charcoal

18. Which of the following is used in cutting tools?
    A. Graphite
    B. Diamond
    C. Coke
    D. Coal

19. The presence of free electrons in graphite makes it:
    A. Hard
    B. Transparent
    C. Conductive
    D. Brittle

20. Which form of carbon is used in water purification?
    A. Activated charcoal
    B. Diamond
    C. Graphite
    D. Fullerene

21. The difference between diamond and graphite is mainly due to:
    A. Atomic number
    B. Number of electrons
    C. Arrangement of atoms
    D. Chemical composition

THEORY QUESTIONS 

1.(a)i. What is Destructive Distillation of Coal 

(ii). Mention the products got from the Destructive Distillation of Coal 

(iii). State one use of each product mentioned above

2. 

1. (a) What is meant by the term allotropy? (2 marks)

(b) Classify the allotropes of carbon into crystalline and non-crystalline forms. Give two examples of each. (4 marks)

(c) State two uses each of:

• Diamond

• Graphite

• Charcoal

             (4 marks) (10 Marks)

2. (a) Describe the structure of diamond and graphite. (4 marks)

(b) Explain why diamond is hard but graphite is soft. (3 marks)

(c) State three differences between diamond and graphite.        (3 marks) (10 Marks)

3.  (a) Name four non-crystalline allotropes of carbon. (4 marks)

(b) Describe how charcoal is produced. (3 marks)

(c) State three uses of charcoal and lampblack (carbon black). (3 marks)(10 Marks)

4.   (a) Distinguish between crystalline and non-crystalline allotropes of carbon. (4 marks)

(b) Explain the electrical conductivity of graphite. (2 marks)

(c) State two uses each of:

• Coke

• Lampblack

• Coal

(4 marks) (10 Marks)

5. (a) Carbon occurs naturally in different allotropic forms. Discuss the properties and uses of the following allotropes:

• Diamond

• Graphite

• Charcoal

• Coke

(8 marks)

(b) State two similarities between diamond and graphite. (2 marks) (10 Marks)

6. (a) Define allotropy and explain why carbon exhibits this phenomenon. (3 marks)

(b) List the crystalline allotropes and non-crystalline allotropes of carbon. (3 marks)

(c) Describe any two crystalline allotropes and any two non-crystalline allotropes of carbon, highlighting their structures, properties, and uses. (4 marks) (10 Marks)