Explanation:
Alkali metals forms the group 1 of the modern periodic table. They include Lithium, sodium, potassium, rubidium, cesium, and francium.
The general electronic configuration of the alkali metals -. They have 1 valence electron.
Ionization energy is the minimum amount of energy which is required to knock out the loosely bound valence electron from the isolated gaseous atom.
<u>Thus, removal of the valence electron leads to the alkali metals having noble gas electronic configuration and which is stable. Thus, the removal of the second electron is very tough and thus, there a large increase between the first and second ionization energies of the alkali metals.</u>