Name a transition element which does not exhibit variable oxidation s…

The correct answer is Option (1) → Sc

Transition elements show variable oxidation states because the (n−1)d and ns electrons have very similar energies, so different numbers of them can be lost or shared. The variety is greatest in the middle of the 3d series and least at the two ends, where there are either too few electrons to lose or too few unpaired d electrons to share.

Scandium (Z = 21) is [Ar]3d¹4s². Losing all three outer electrons gives \( \ce{Sc^{3+}} \) with the stable argon configuration, [Ar]. Losing fewer electrons gives no such stability, and scandium(II) is virtually unknown. So scandium shows only the +3 oxidation state and is the transition element that does not exhibit variable oxidation states. (Zinc also shows only +2, but with its completely filled 3d¹⁰ set it is not regarded as a transition element.)

NCERT (2026-27 edition):
Oxidation States – …