What electron configurations do atoms usually achieve by sharing electrons to form covalent bonds?

Explanation: The atoms attain the configuration of inert gas by sharing electrons.

Lets take an example of HCl,

Atomic number of H is 1 and it has only 1 valance electron. whereas atomic number of chlorine is 17 and it has 7 valance electron.

When hydrogen atom combine with chlorine atom then they share electrons through covalent bonding in order to complete their octet.

According to figure,

Electronic configuration of H = 1

Electronic configuration of Cl = 2,8,7

Now, after share of electron

Electronic configuration of H = 2

Electronic configuration of Cl = 2,8,8

Hence, we can conclude that when atoms share electrons then their octet gets complete and atoms achieve noble gas electronic configuration.