Why is the first ionization energy of a nonmetal much higher than that of an alkali metal in its same period?

Answer and explanation;Ionization Energy is the energy required to remove an electron from an atom in its gaseous state. The first ionization tends to decrease from top to bottom within a group and increase from left to right across a period.The atoms of the alkali metals have larger radii than those of nonmetals. Because of this, the attraction of the positively charged atomic nucleus for the valence electron is much less than that of a nonmetal.Therefore, the first ionization energy of an alkali metal is much less than that of a nonmetal. Because of this, alkali metals lose their single valence electron which produces a cation with a charge of +1. The atoms of nonmetals have smaller radii, therefore the positively charged nucleus has a greater attraction for the valence electrons.