Alkali metals have one electron in their outer shell, which is loosely bound. This gives them the largest atomic radii of the elements in their respective periods. Their low ionization energies result in their metallic properties and high reactivities.
Madam, I have 2 doubts-firstly, what is ionization energy and secondly what are alkali metals?
Ionization Energy: The ionization energy is the minimum energy required to remove an electron from the ground state of the isolated gaseous atom.
It is basically the measure of how strongly an atom holds its electrons.
The alkali metals are a series of chemical elements forming Group 1 (IUPAC style) of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb),caesium (Cs), and francium (Fr).
We hope that clarifies your query.