Identify the alkali metal having the smallest atomic size from the following.

$(a)$ Describe the chemical properties of alkali metals with air,water,dihydrogen,and halogens.
$(b)$ Explain the reduction potential of alkali metal elements.
$(c)$ Which type of solutions are formed on the reaction of alkali metals with liquid ammonia?

In the preparation of sodium carbonate,which of the following is used?

The solution of sodium metal in liquid ammonia is a strong reducing agent due to the presence of:

Identify the correct order of standard enthalpy of formation of sodium halides.

$KO_2$ (potassium superoxide) is used in oxygen cylinders in space and submarines because it