When an atom gains an electron to form an anion, the size typically:

When an atom gains an electron to form an anion, the size typically:

• A. Decreases
• B. Increases
• C. Remains the same
• D. Fluctuates

Answer: (B)

When an atom gains electrons, the number of electrons increases while the nucleus stays the same. The added electrons boost repulsion within the electron cloud and increase shielding, so the outer electrons experience less pull from the nucleus. With less effective nuclear attraction and more repulsion pushing the cloud outward, the electron cloud expands. That makes the ionic radius larger for an anion than for the neutral atom. (In contrast, losing electrons to form a cation reduces repulsion and typically shrinks the radius.)

When an atom gains electrons, the number of electrons increases while the nucleus stays the same. The added electrons boost repulsion within the electron cloud and increase shielding, so the outer electrons experience less pull from the nucleus. With less effective nuclear attraction and more repulsion pushing the cloud outward, the electron cloud expands. That makes the ionic radius larger for an anion than for the neutral atom. (In contrast, losing electrons to form a cation reduces repulsion and typically shrinks the radius.)