multiple - choice question\nchoose the atom with the highest ionization energy.\nsi\nmg\ncl

Brief Explanations:

Ionization energy increases across a period from left - to - right in the periodic table. Si (silicon), Mg (magnesium), and Cl (chlorine) are in the same period. Mg is in group 2, Si is in group 14, and Cl is in group 17. As we move from left to right, the effective nuclear charge increases, making it harder to remove an electron and thus increasing ionization energy.

Answer:

C. Cl