ACKNOWLEDGEMENT:
Figure
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Source of Figure
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Figure 15
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www.gcsescience.com
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Table 6a
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www.bbc.co.uk
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Table 6b
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www.bbc.co.uk
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Table 6c
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www.bbc.co.uk
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Table 6d
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www.bbc.co.uk
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Table 6e
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Ibchem.com
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Table 6f
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www.bbc.co.uk
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Table 6g
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www.bbc.co.uk
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Table 6h
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www.gcsescience.com
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Table 6i
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www.bbc.co.uk
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Table 6j
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www.bbc.co.uk
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Covalent Compounds:
Covalent compounds are formed between non-metals by the sharing
of valence electrons. This type of bonding can be classified into:
i.
Simple
molecular bonding
ii.
Macro
molecular bonding
Simple Molecular
Bonding:
Some compounds are formed by the reactions between non-metals to
attain the noble gas electronic configuration by electron sharing. These bonds formed
are not very strong and thus covalent compounds of this type have low melting
and boiling points. Since, electrons are shared, and ions are absent, these
compounds are non-conductors of electricity.
Consider the example of methane for understanding electron
sharing in covalent compounds.
Figure 16:
The Carbon atom contain 4 valence electrons and requires 4
electrons to fill its valence shell. Hydrogen atom contains 1 electron in the K
shell and require 1 more electron to fill its valence shell. By electron
sharing, the compound of methane, CH4 is formed. In this, the
valence shell of carbon is filled by the shared electrons of 4 atoms of
hydrogen and the valence shell of each hydrogen is filled with 2 electrons.
Thus, the valency of both the elements is satisfied. The absence of ions makes
simple covalent compounds a non-conductor and the weak Vander Walls forces
account for the low melting and boiling points.
Table 6: Some common simple covalent compounds and
their dot and cross models
H2
|
 |
Cl2
|
 |
O2
|
 |
HCl
|
 |
N2
|
 |
H2O
|
 |
CH4
|
 |
C2H6
|
 |
CO2
|
 |
NH3
|
 |
Table 7: Properties of
Simple Covalent Compounds
Property
|
Reason
|
Low melting and Boiling points
|
Weak Vander Walls
forces of attraction between the shared electrons
|
Non-Conductors of electricity
|
Covalent compounds
are non-conductors of electricity in any state as the electrons shared CANNOT
move, and neither ions nor free electrons are present to carry the electric
current
|
