In a covalent bond, the shared electrons are attracted to the nuclei of both atoms, creating a strong bond.
Occurs in most non-metallic elements and in compounds of nonmetals
Strong bonds between atoms that are covalently bonded are the result of electrostatic attraction between the positive nuclei of the atoms and the pairs of negative electrons that are shared between them
Substances that consists of small molecules:
Are usually gases or liquids that have low boiling and melting points
Have weak intermolecular forces between the molecules
These are broken in boiling melting, not the covalent bonds
Don't conduct electricity
As the small molecules do not have an overall electric charge
Intermolecular forces increase with the size of the molecules
The larger the molecules, the higher the melting and boiling points
Substances that consist of giant covalent structure are all solids with very high melting points
All the atoms are linked to other atoms by strong covalent bonds
Bonds must be overcome to melt or boil these substances
Diamond
Each carbon covalently joined to 4 other carbons
Very hard
Very high melting point
Does not conduct electricity
Graphite
Each carbon is covalently bonded to 3 other carbons
Forming layers of hexagonal rings
Weak intermolecular forces between the layers
No covalent bonds between the layers
= soft and slippery
One electron from each carbon is delocalized
Conduct electricity
Graphene
Single layer of graphite
Has properties that make it useful in electronics and composites
Fullerenes
Molecules of carbon atom with hollow shapes
Based on hexagonal rings of carbon atoms
May also contain rings with 5 or 7 carbon atoms
First fullerene to be discovered was Buckminsterfullerene (C60)
Spherical shape
Carbon nanotubes
Cylindrical fullerenes with very high length to diameter ratios
There properties make them useful for nanotechnology, electronics and materials
Covalent compounds don't conduct electricity except graphite and graphene