What are the conditions necessary for the formation of covalent molecule? Give their properties.
Necessary conditions for the formation of covalent molecules:
(1) Presence of four or more valence electrons in both the combining atoms.
(2) Equal electronegativity of the combining atoms.
(3) Equal electron affinity of the combining atoms.
(4) The combining atoms should have high ionisation energy.
(5) The combining atoms should have small internuclear distance and high nuclear charge.
Properties of covalent molecules:
(1) They are generally volatile liquids or gases.
(2) They have low melting and boiling points.
(3) They do not conduct electricity.
(4) They are generally soluble in organic solvents and insoluble in water
(5) They do not ionise when dissolved in water.
(6) All the atoms in molecule of a covalent compound participate in molecular reactions.