Which of the following is the atomic number of a metal?

The properties of $Li$ are similar to those of $Mg$. What is the reason for this?

Statement $A$: Extraction of magnesium is done by the electrolysis of a molten mixture of $MgCl_2$,$NaCl$,and $CaCl_2$.
Reason $R$: Calcium chloride acts as a reducing agent.

Assertion $(A)$: $K$,$Rb$,and $Cs$ form superoxides.
Reason $(R)$: The stability of the superoxides increases from $K$ to $Cs$ due to the decrease in lattice energy.
The correct answer is:

The lightest metal is

Which of the following salts form hydrates? $CaCl_2$ $(I)$,$NaCl$ $(II)$,$LiCl$ $(III)$,$BaCl_2$ $(IV)$,$KCl$ $(V)$