Question

Why do alkali metals have low melting and boiling points ?

Answer 1

The chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr) make up the alkali metals (Fr). They make up group 1, which is located in the s-block of the periodic table, along with hydrogen. The outermost electron of all alkali metals is in an s-orbital configuration; as a result of this shared electron configuration, their distinctive characteristics are remarkably similar.

Complete Step By Step Answer:
The fact that alkali metals have a $n{{s}^{1}}$ valence electron configuration, which results in weak metallic bonding, explains their physical and chemical characteristics. As a result, all alkali metals are soft, with low densities, melting temperatures, and boiling points.
The nucleus of all Group 1 elements has one electron in its outermost shell, which is retained extremely weakly. In most atoms of other elements, this electron can travel further from the nucleus. As a result, the atomic radii of Group 1 elements are greater than those of the elements that come after them in their respective periods. Because of the high atomic scale, the forces between neighbouring atoms are less. When compared to other metals, Group 1 elements have lower melting and boiling temperatures due to weaker attraction interactions caused by greater atomic radii between nearby atoms.
The increase in atomic radius caused by the addition of a shell to the previous element explains the reduction in melting and boiling points along the group. As the atomic radius grows, the interactions between the atoms weaken, resulting in a lower melting and boiling point. Because of weak metallic connections caused by larger atomic sizes, they have low melting and boiling points.

Note:
A substance's boiling point is the temperature at which the vapour pressure of a liquid equals the pressure around the liquid and the liquid transforms into a vapour. A substance's melting point is the temperature at which it transitions from solid to liquid condition. The solid and liquid phases are in balance at the melting point.