CBSE Class 10 Science 2017 · Paper 31/1/2/C · Question 7

(a) Electronic configuration of M: $2,8,8,1$ (K, L, M and N shells). Valency: $1$. (b) M is a metal: it has only one electron in its outermost shell, which it loses readily to form the positive ion ${\text{M}}^{+}$, as metals do. (c) Formula of the oxide: ${\text{M}}_2\text{O}$ (M is potassium, so the oxide is ${\text{K}}_2\text{O}$). Nature: basic; it dissolves in water to form the alkali $\text{MOH}$.