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

Which of the following alloys are correctly matched with their uses?
$(i)$ $Li-Mg$ armour plates
$(ii)$ $Cu-Be$ high strength springs
$(iii)$ $Mg-Al$ aircraft construction

Alkali metals react with water to form hydroxides and release hydrogen gas. This is because:

The lightest metal is

What is the product formed when sodium nitrate is heated at a temperature of ${800\,^o}C$?

Which of the following is an alkali metal?