The correct order of decreasing electronegativity values among the elements I-beryllium, II-oxygen, III-nitrogen and IV-magnesium, is (Kerala CEE 2011)

Electronegativity is the measure of the tendency of an atom to attract the bonding pair of electrons towards them. The trend of electronegativity decreases down the group due to an increase in atomic radius and increases from left to right in the period due to a decrease in size. Therefore, the correct is Oxygen > Nitrogen > Beryllium > Magnesium or (II) > (III) > (I) > (IV)