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
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 with elongated shapes. The Carbon atoms are arranged in hexagons and pentagons
The most common fullerene is Buckminsterfullerene (C₆₀), which has a spherical shape like a football
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
The carbon atoms are arranged in closed hollow structures such as spheres, ellipsoids, or tubes.
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 – produced when wood, bones or blood is burnt in limited supply of air/oxygen.
Types of charcoal
a. Wood charcoal
b. sugar charcoal
c. animal charcoal
Uses
i. absorbs gases and colours
ii. as fuel
iii. Coal – formed during the carboniferous era from from incomplete decomposed vegetations
Types of Coal (check post on coal):
there are four stages of coal
i. Peat – about 60% carbon
ii. Lignite – about 67% carbon
iii. Bituminous – about 88% carbon
iv. Anthracite – about 94% carbon. (hardest and purest form)
Destructive Distillation of Coal:- This is when coal is heated to a very high temperature in the absence of air.
The products got are a
Coal → Coal gas + Coal tar + Ammoniacal liquor + Coke
Gasification of coke: when coke is heated until it is red hot or white hot and air or 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) + O2/N2→ CO + N2
ii.Water gas: Produce when steam is blown over red-hot coke C(s) + H2O(l) → CO + H2
iii. Synthetic gas: C(s) + H2O → CO + H2
ii. Carbon black & lampblack – used in tyres, inks and polish
i.
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 and triple covalent bond)
iii. Flexibility in bonding arrangements
Chemical Properties of Carbon
i. Carbon burns in oxygen to form CO2 or CO
C(s) + O2(s) → CO(g) (limited oxygen)
C(s)
ii. With sulphur
C(s) + S(s) → CS2
iii. Acts as a reducing agent in metal extraction
iv. Fe2O3 + C(s) → Fe(s) + CO2(g)
Is oxidized by strong acids to form CO2
2H2SO4(aq) + C(s) → 2SO2(g) + 2H2O(g) + CO2(s)
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
D. Linear
9. Which allotrope of carbon is used as a lubricant?
A. Diamond
B. Graphite
C. Coal
D. Coke
10.The black soot obtained from incomplete combustion is called:
A. Coke
B. Charcoal
C. Lampblack
D. Coal tar
11 Which allotrope of carbon is the hardest natural substance?
A. Graphite
B. Diamond
C. Coke
D. Charcoal
12. Fullerenes are composed of carbon atoms arranged in:
A. Chains
B. Sheets
C. Spherical shapes
D. Cubes
13. Which of the following is NOT an allotrope of carbon
A. Graphene
B. Diamond
C. Silicon
D. Fullerene
14. The valency of carbon is
A. 2
B. 3
C. 4
D. 6
15. Coal is mainly composed of
A. Hydrogen
B. Oxygen
C. Carbon
D. Nitrogen
16. Which allotrope has a layered structure with weak forces between layers?
A. Diamond
B. Graphite
C. Fullerene
D. Charcoal
17. Which of the following is used in cutting tools?
A. Graphite
B. Diamond
C. Coke
D. Coal
18. The presence of free electrons in graphite makes it:
A. Hard
B. Transparent
C. Conductive
D. Brittle
19. Which form of carbon is used in water purification?
A. Activated charcoal
B. Diamond
C. Graphite
D. Fullerene
20. 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. . (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:
i. Diamond
ii. Graphite
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:
i. Coke
ii. Lampblack
5. (a) Carbon occurs naturally in different allotropic forms. Discuss the properties and uses of the following allotropes:
i. Diamond
(b) State two similarities between diamond and graphite.
6. (a) Define allotropy and explain why carbon exhibits this phenomenon.
(b) List the crystalline allotropes and non-crystalline allotropes of carbon.
(c) Describe any two crystalline allotropes and any two non-crystalline allotropes of carbon, highlighting their structures, properties, and uses.