How many electrons form a covalent bond?
Answers
A minimum of two atoms must combine to form a compound. These atoms must be mutually connected and in the case of covalent bonds where the difference in electronegativity is moderate or low, sufficient energy is not present to transfer an electron from one atom to another.
Think of covalent bonding as a mutual compromise. Two people are working together towards a common goal may pool in their combined resources to help them better achieve that goal. Just like that each atom shares 1 electron to form a pair.
But you might ask, why not 3 or 4 then ?
The reason for that is actually the relation between inter-electron repulsion and the attraction between a nucleus and and electron. In the arrangement of an electron pair as shown below, the net force of attraction is such that they are roughly in equilibrium state.