Be has 2 electrons in its outer shell, O has 6 electrons in its outer shell. Choose the correct option:
Be and O have valency 2 and 2 respectively
Valency of an atom is the number of electrons it is willing to give up or the number of electrons it is willing to accept in order to achieve the electronic configuration of nearest stable noble gas. Here if Beryllium gives up two electrons, it achieves the configuration of Helium which is stable. So the valency of Beryllium is 2.
Similarly, Oxygen accepts 2 electrons to achieve the configuration of Argon. So the valency of Oxygen is 2.