Which of the following substances is the least soluble in water?

Which of the following is the weakest base among $NaOH$,$Ca(OH)_2$,$KOH$,and $Ba(OH)_2$?

$Beryllium$ shows a diagonal relationship with:

Why does the solubility of alkaline earth metal carbonates and sulphates decrease down the group?

$Mg(NO_3)_2 \cdot XH_2O$ and $Ba(NO_3)_2 \cdot YH_2O$ represent the formulas of the crystalline forms of nitrate salts. The sum of $X$ and $Y$ is $.........$.

Which of the following properties of the alkaline earth metals increase from $Be$ to $Ba$?
$(i)$ Atomic radius
$(ii)$ Ionisation energy
$(iii)$ Nuclear charge