An atom of oxygen has six electrons in its outermost ring and requires two more to become stable. What is the valence number of oxygen

Oxygen in its natural state has 6 valence electrons.

Explanation: The atomic number/ proton number of oxygen is 8, as seen on the periodic table. This is equal to the electron number.

This means there are 2 electrons in the core s shell (innermost), and 6 electrons in the p shell (outermost).

Valence electrons are the electrons found in the outermost shell, so Oxygen has 6 valence electrons.

I don't know if you've been taught electron configuration, but Oxygen's electron configuration is: . The 2s and 2p are orbitals of the outermost ring in Oxygen, so adding 2+4 = 6 valence electrons.