Question

(a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?

Answer 1

Element	Electronic configuration	Valence electrons	Group
$Li\left(3\right)$	$2,1$	$1$	$1$
$Na\left(11\right)$	$2,8,1$	$1$	$1$
$K\left(19\right)$	$2,8,8,1$	$1$	$1$

1) All these metals have one valence electron in their outermost shells and as a result of this, they are very unstable.
2) So, they readily react with water to liberate hydrogen. They are also called alkali metals.