Which of the following atoms or ions is the smallest?

Question

Quizplus · Accepted Answer

The size of atoms and ions decreases across a period due to the increase in nuclear charge, which pulls the electrons closer to the nucleus. Among the given options, Mg^2+ (option D) is the smallest because it is a cation with a +2 charge, which significantly reduces its radius compared to its neutral atom form and compared to other ions and atoms listed. Additionally, being in the second period, it has fewer electron shells than options involving elements from lower periods or with less positive charge.

Which of the Following Atoms or Ions Is the Smallest