EVERYDAY SCIENCE

Detailed explanation-1: -whereas the valence electrons in magnesium are found in the Mth shell and are being shielded by only K and L shells and hence experience greater attraction to the nucleus and hence require more energy to remove.

Detailed explanation-2: -Thus the outer electrons in calcium are less well shielded and are harder to remove. In addition, a calcium atom has a smaller radius than a potassium atom, making it even harder to remove one of its outer (4s) electrons. [e] Remember that, across a period, the atomic radius decreases as the atomic number increases.

Detailed explanation-3: -Among the chemical elements of any period, removal of an electron is hardest for the noble gases and easiest for the alkali metals.

Detailed explanation-4: -The second ionization energy of Mg is larger than the first because it always takes more energy to remove an electron from a positively charged ion than from a neutral atom. The third ionization energy of magnesium is enormous, however, because the Mg2+ ion has a filled-shell electron configuration.