With an increase in atomic number,the melting point of alkali metals $...$

The $s$-block elements are characterised by their larger atomic sizes,lower ionisation enthalpies,invariable $+1$ oxidation state and solubilities of their oxosalts. In the light of these features,describe the nature of their oxides,halides and oxosalts.

Magnesium burns in air to give

The element which cannot form peroxide is

Which of the following alkali metal ions has the lowest ionic mobility in an aqueous solution?

Which of the following is $CORRECT$ regarding alkali metals?
$I$. Pure $NaCl$ is hygroscopic
$II$. $(n - 1)d$ subshell is vacant only
$III$. Aqueous $NaHCO_3$ solution is more basic than $Na_2CO_3$ solution
$IV$. Both $Li^{+}$ and $Mg^{2+}$ do not form alums