Which of the following formulas represents lithium imide?

The golden yellow colour associated with $NaCl$ in a Bunsen flame can be explained on the basis of

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.

The valence shell electronic configuration of alkali metals is

Caesium is used in

Chile saltpetre is