10.30 Which of the alkali metal is having least melting point ? (a) Na (b) K (c) Rb (d) Cs

Answers (1)
R Rakesh

The strength of metallic bond decreases down the group in the periodic table because as the size of cation increases the binding energies of their atoms in the crystal lattice decreases. 

order of melting point  Na>k>Rb>Cs  

So, ans is (a) Na