Explain briefly how +2 state becomes more and more stable in the first half of the first-row transition elements with increasing atomic number?

Question

Philoid · Accepted Answer

The oxidation states displayed by the first half of the first row of transition metals are given in the table below.

METALS	Sc([Ar] 3d¹4s²)	Ti([Ar] 3d²4s²)	V([Ar] 3d³4s² )	Cr([Ar] 3d⁵4s¹)	Mn([Ar] 3d⁵4s²)
OXIDATION STATES		+2	+2	+2	+2
	+3	+3	+3	+3	+3
		+4	+4	+4	+4
			+5	+5	+6
				+6	+7

Except for Sc, all others metals display +2 oxidation state. This is because as the atomic number increases, the number of electrons in the valence shell increases. +2 oxidation state is attained by the loss of the two 4s electrons by these metals. As the number of electron increases, the possibility of an ion with +2 oxidation state being stable(by attaining half-filled structure) also increases. Finally, Mn²⁺ ions have half-filled structure and are very stable.