An unknown element, x, reacts with sodium to form the compound na2x. in other compounds this element also can accommodate up to 12 electrons rather than the usual octet. what element could x be?
a) be
b) ai
c) f
d) ci
e) sc
f) as
g) y

e) Sc and g) Y.

Explanation:

An ionic compound is formed by the ions, which their charges replaced, so the compound Na₂X is formed by the ions Na⁺ and X⁻². Thus, X must gain two electrons to be stable at the octet, so it has 6 valence electrons. Because it can accommodate up to 12 electrons, the element expands the octet, do it must be in the 3rd period or higher.

So, X can be Sc or Y.