The compound$(s)$ formed upon combustion of sodium metal in excess air is(are):

The atomic radii of the alkali metals follow the order

When $NaOH$ crystals are left in open air,they acquire a fluid layer around each crystal because:

Among the hydroxides and carbonates of $IA$ and $IIA$ group elements respectively,on moving down the group,the correct solubility order is:

The correct order of conductivity of ions in water is

The correct order of electropositive nature of $Li$,$Na$ and $K$ is