Question

1. which particle has the larger radius in each atom - ion pair?

a) na or na+
b) s or s^{2 - }
c) i or i^{-}
d) al or al^{3 + }

Explanation:

Step1: Analyze the principle of atomic and ionic radius

When an atom loses electrons to form a cation, the number of electrons decreases while the nuclear charge remains the same. The remaining electrons are more strongly attracted by the nucleus, so the radius of the cation is smaller than that of the corresponding atom. When an atom gains electrons to form an anion, the number of electrons increases. The mutual repulsion between electrons increases, and the radius of the anion is larger than that of the corresponding atom.

Step2: Analyze each pair

• For \(Na\) and \(Na^{+}\): \(Na\) loses one electron to form \(Na^{+}\). According to the above principle, \(Na\) has a larger radius.
• For \(S\) and \(S^{2 - }\): \(S\) gains two electrons to form \(S^{2 - }\). According to the above principle, \(S^{2 - }\) has a larger radius.
• For \(I\) and \(I^{-}\): \(I\) gains one electron to form \(I^{-}\). According to the above principle, \(I^{-}\) has a larger radius.
• For \(Al\) and \(Al^{3+}\): \(Al\) loses three electrons to form \(Al^{3+}\). According to the above principle, \(Al\) has a larger radius.

Answer:

a) \(Na\); b) \(S^{2 - }\); c) \(I^{-}\); d) \(Al\)