Question

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

Answer 1

Element (+2 state) ${}_{21}S{c}^{2+}{}_{22}T{i}^{2+}{}_{23}{V}^{2+}{}_{24}C{r}^{2+}{}_{25}M{n}^{2+}$

Electronic configuration $3d^{1}3d^{2}3d^{3}3d^{4}3d^5$

In all the elements listed, the removal of two 4s electrons (in $C{r}^{2+}$ i.e., from 4s and $1e^{-}$ from 3d), the 3d-orbitals get gradually occupied. Since, the number of empty d-orbitals decreases or the number of unpaired electrons in 3d-orbitals increases with increase in atomic number of cations, so the stability of the cations $\left(M^{2+}\right)$ increases from $S{c}^{2+}$ to $M{n}^{2+}$