Carbon and its compounds

Question 1

Percentage of carbon in the environment

Answer 1

The earth’s crust has only
0.02% carbon in the form of minerals (like carbonates, hydrogencarbonates, coal and petroleum) and the atmosphere has 0.03% of carbon
dioxide. In spite of this small amount of carbon available in nature, the
importance of carbon seems to be immense

Question 2

General note about carbon

Answer 2

Atomic number -6
atomic weight-12 u
Electronic configuration-2,4

Question 3

What is a covalent bond

Answer 3

A covalent bond is a chemical bond that occurs when two or more atoms share electrons .The atoms could be of same or different species

Question 4

How many types of covalent bond exist in nature

Answer 4

Single covalent bond-One pair of electrons is shared between the atoms ,for example chlorine molecule
Double covalent bond-Two pair of electrons are shared among the atoms , for example Oxygen molecule
Triple covalent Bond-Three pair of electrons are shared among the atoms , for example nitrogen molecule

Question 5

Why can’t carbon form ions

Answer 5

(i) It could gain four electrons forming C4– anion. But it would be difficult
for the nucleus with six protons to hold on to ten electrons, that is,
four extra electrons.
(ii) It could lose four electrons forming C4+ cation. But it would require
a large amount of energy to remove four electrons leaving behind a
carbon cation with six protons in its nucleus holding on to just two
electrons.

Question 6

Physical properties of carbon

Answer 6

1. Have no free electrons or ions therefore they are poor conductors of electricity .
   2.In general covalent bonds are strong but the intermolecular attraction is weak and hence they have low melting and boiling point

Question 7

Allotropes

Answer 7

Form of carbon which have similar chemical properties but different physical properties.
Can be further classified into amorphous and crystalline form

Question 8

Crystalline form

Answer 8

GRAPHITE:
In graphite, each carbon atom is bonded to three
other carbon atoms in the same plane giving a hexagonal array.
One of these bonds is a double-bond, and thus the valency of carbon is satisfied. Graphite structure is formed by the
hexagonal arrays being placed in layers one above the other.
Graphite is also a very good conductor of electricity unlike other non-metals

DIAMOND:

In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure
. Diamond is the hardest substance known

Fullerene:

Fullerenes form another class of carbon allotropes. The first one to be identified was
C-60 which has carbon atoms arranged in the shape of a football. Since this looked
like the geodesic dome designed by the US architect Buckminster Fuller, the molecule
was named fullerene.