JEE Main · 2020 · 04 Sep 2020 · Shift 2 · s-Block Elements

The metal whose sulphate is water soluble while its hydroxide is insoluble, and whose oxide is unusually stable to heat and avoids the rock-salt structure, is beryllium. $\mathrm{BeS}{\mathrm{O}}_4$ dissolves readily, unlike the sparingly soluble sulphates lower in the group, $\mathrm{Be}(\mathrm{OH}{)}_2$ is insoluble, and $\mathrm{BeO}$ is exceptionally refractory and crystallises in the hexagonal wurtzite lattice rather than the rock-salt structure of $\mathrm{MgO}$ or $\mathrm{CaO}$. These anomalous properties identify $M$ as beryllium.