State the number of electrons lost or gained when the following elements form

Question

Ions:
Se

Answer 1

Selenium is in Group 16 of the periodic table, so it has 6 valence electrons.

In order to form ions, elements tend to gain or lose electrons in order to achieve a stable electron configuration, usually with a full outer shell of 8 electrons (except for hydrogen and helium which only need 2 electrons in their outer shell).

Selenium can either gain 2 electrons to achieve the stable electron configuration of argon (Ar), or it can lose 6 electrons to achieve the stable electron configuration of krypton (Kr).

Therefore, when selenium forms ions, it can either gain 2 electrons or lose 6 electrons.