Why is the ground state electron configuration for arsenic consistent with Na3AS, AsCl3, and Asf5 ???

Question

As [Ar] 4s2 3d10 4p3

Answer 1

Since there are 5 electrons (2 4s's and 3 4p's) arsenic can combine with a very electropositive element (Na) and gain 3 to fill it's octet. It can react with an electronegative element (Cl) and share electrons, so both elements have their octets filled and it can react with a very electronegative element (F) and loose the 5 valence electrons instead of gaining 3.