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Covalent Bonding (Simple molecular structures (Physical properties of…
Covalent
Bonding
Simple molecular structures
Physical properties of substances with simple molecular structures
most
do not conduct electricity in all 3 states
Have low melting and boiling point
usually
insoluble in water and soluble in organic solvents
Most covalent substances
such as bromine
exist as simple molecules
Giant molecular structures
Physical properties of substances with giant molecular structures
it have high melting and boiling points
It does not conduct electricity
(except graphite)
It is
insoluble in both water and organic convents
Some substances exist as a giant network of atoms that are covalently bonded
E.g diamonds and graphite
both are
allotropes
of carbon(diff forms of carbon)
Diamond is hard and has high melting point
Each carbon atom covalently bond to 4 other carbon atoms ,forming 3D structure which is difficult to bring this strong covalent bonds
Diamond does not conduct electricity
Outer electron of carbon atom are used for bonding. Hence
no free electron that move through structure to conduct electricity
Graphite has high melting and boiling point
Each carbon atom is covalently Bonner to 3 other carbon atoms,
forming continuous layer of hexagons
Graphite is soft and slippery
Layers of carbon atoms hold loosely by
weak intermolecular forces of attraction
allowing atoms able to slide over each other when force applied
Graphite conducts electricity
Carbon atom has one outer electron that is not used to fork covalent bonds, hence
these electrons can move freely along the layers from one carbon to another.
They are said to be delocalised allowing graphite to conduct electricity
Silicon dioxide has high melting and boiling point
Each silicon atom is boned to 4 oxygen atoms and each oxygen atom is boned to 2 silicon atoms forming 3D
which is difficult to break the bond
Silicon dioxide does not conduct electricity
There are
no free elections
that move through structure to conduct electricity