Which one of the following is an oxide?

Sodium reacts more vigorously with water than lithium because...

Which of the following statements are correct for alkali metal compounds?
$(i)$ Superoxides are paramagnetic in nature.
(ii) The basic strengths of hydroxides increase down the group.
(iii) The conductivity of chlorides in their aqueous solutions decreases down the group.
(iv) The basic nature of carbonates in aqueous solutions is due to cationic hydrolysis.

Which of the following statements is not correct for the element having electronic configuration $1s^2, 2s^2 2p^6, 3s^1$?

The electronic configuration of $Cs$ is

In the Solvay process,can we obtain sodium carbonate directly by treating the solution containing $(NH_4)_2CO_3$ with sodium chloride? Explain.