Question

The configuration of Fetion in the ground state is
(a) [Ar]3d42
(b) [Ar]3d42
(c) [Ar]3d
(d) [Ar]3d​

Answer 1

The question is not fully clear, but I will give the configurations of Fe metal, and Fe ion in both its oxidation states.

Fe (metal): (Atomic No 26) ----> [Ar]4s2 3d4

$Fe^{2+}$ ion ------> [Ar]3d4 (remember the 4s electrons get removed first)

$Fe^{3+}$ ion ------> [Ar]3d3 (two electrons from 4s, one electron from 3d)

Hope it helps!!!