Question

Melting point of lithium is just double than sodium because

Answer 1

Answer:

Melting point decreases going from lithium to sodium because sodium is lower down group one therefore it has a greater number of shells. A greater number of shells means a greater atomic radius - a greater shielding effect of the inner shells. This makes it easier to remove an electron from the outer shell of electrons because there is a lower nuclear attraction.

Answer 2

Answer:

Both are alkali metals, both with one electron on the external electron shell. A difference between them is that Lithium (with 2 electron shells) is crystallised in a denser configuration than Sodium (with 3 electron shells), i.e. stronger forces between the atoms.