How many valence electron does oxygen contain? How many electrons will it share with another oxygen atom?
Valence electron of oxygen is 6 and each oxygen atom will share 4 valence electrons to make a double bond with another oxygen atom.
Valence electron of oxygen is 6 and in order to attain octet configuration (i.e.8 valence electron), it needs to share 2 more electrons. i.e. each oxygen atom will share 2 electrons.
Thus, a total number of electrons shared is 4 and unshared electrons are 4 and thus attains octet configuration.