The atomic radius of Halogens is smaller than the ionic radius.

This is because they react by gaining/acquiring extra one electron in the outer energy level.

The effective nuclear attraction on the more/extra electrons decreases.

The incoming extra electron is also repelled causing the outer energy level to expand to reduce the repulsion and accommodate more electrons.

The atomic radius of Chlorine is  0.099nM .The ionic radius of Cl- is 0.181nM.

This is because Chlorine atom/molecule reacts by gaining/acquiring extra one electrons.

The more/extra electrons/energy level experience less effective nuclear attraction /pull towards the nucleus .

The outer energy level expand/increase to reduce the repulsion of the existing and incoming gained /acquired electrons.

Electronegativity

The ease of gaining/acquiring extra electrons is called electronegativity.

 All halogens are electronegative. Electronegativity decreases as atomic radius increase.

This is because the effective nuclear attraction on outer     electrons decreases with increase in atomic radius.

The outer electrons experience less nuclear attraction and thus ease of gaining/acquiring extra electrons decrease.

It is measured using Pauling’s scale.

Where Fluorine with Pauling scale 4.0 is the most electronegative element  and thus the highest tendency to acquire/gain extra electron.

    Table showing the electronegativity of the halogens.

The electronegativity of the halogens decrease down the group from fluorine to Astatine. Explain