JEE Main · 2019 · 11 Jan 2019 · Shift 1 · d and f Block Elements

Scandium has the configuration $[\mathrm{Ar}]3d^{1}4s^2$, and once it loses those three outer electrons it reaches the stable argon core as $\mathrm{Sc}{}^{3+}$. With nothing left to vary, it shows essentially only the $+3$ state. Titanium, vanadium and copper still have $d$-electrons to gain or lose and so display several oxidation states; scandium is the one that does not.