Question

A first row transition metal with the highest enthalpy of atomisation, upon reaction with oxygen at high temperature, forms oxides of formula $\text{M}_2\text{O}_n$ (where $n = 3, 4, 5$). The 'spin-only' magnetic moment value of the amphoteric oxide from the above oxides is ___ BM (near integer).
(Given atomic number: $\text{Sc: 21, Ti: 22, V: 23, Cr: 24, Mn: 25, Fe: 26, Co: 27, Ni: 28, Cu: 29, Zn: 30}$)

Answer 1

Vanadium (V) has the highest enthalpy of atomisation (515 kJ/mol) among first-row transition elements. When it forms an oxide, it produces $\text{V}_2\text{O}_5$.
In $\text{V}_2\text{O}_5$:
Vanadium is in the $+5$ oxidation state.
The electron configuration of $\text{V}^{5+}$ is $1s^2 2s^2 2p^6 3s^2 3p^6$, with no unpaired electrons.
Since there are no unpaired electrons in $\text{V}^{5+}$, the "spin-only" magnetic moment is zero.