1.49 understand why covalent compounds do not conduct electricity

In a covalent compound, there are no delocalised electrons, so it cannot hold a current. Graphite is an exception, as this is a giant covalent structure and has the 4th electron free to move, so graphite can conduct electricity.

1.40 explain, using dot and cross diagrams, the formation of covalent compounds by electron sharing for the following substances:

i hydrogen

ii chlorine

iii hydrogen chloride

iv water
Just one example of a dot cross diagram.


v methane

vi ammonia

vii oxygen

viii nitrogen

ix carbon dioxide

x ethane

xi ethene

1.39 understand covalent bonding as a strong attraction between the bonding pair of electrons and the nuclei of the atoms involved in the bond

Covalent bonding part II

During covalent bonding, the sharing of electrons between 2 non-metals, the electrons become attracted to the nucleus of each ion in a bond, this is electrostatic attraction.

1.38 describe the formation of a covalent bond by the sharing of a pair of electrons between two atoms

Covalent bonds

When two non-metallic elements combine together they often share  electrons between them. When an atom of hydrogen, H and an atom of chlorine, Cl, combine to form hydrogen chloride, HCl, the atoms come close enough together for their outer electron (valence) shells to overlap.