Question

Which particle has the larger radius in each atom/ion pair?

a) Na, Na
b) S, S^-2
c) I, I^-
d) Al, Al^3

Answer 1

In comparing the radii of atoms and their ions, cations are smaller and anions are larger than their neutral parent atoms. Na+ and Al3+ are cations and thus smaller than Na and Al, respectively, while S2- and I- are anions and larger than S and I, respectively.

Step-by-step explanation:

The question asks about comparing the radii of atoms and their corresponding ions. It's important to remember that cations are always smaller than their parent atoms, because they have lost one or more electrons which reduces electron-electron repulsion and allows the electrons to be pulled closer to the nucleus. In contrast, anions are always larger than their parent atoms because they have gained electrons, increasing electron-electron repulsion which forces the electrons to move further apart.

We can apply this general rule to answer each of the pairs:

1. Na vs. Na+: The Na+ ion will have a smaller radius than the neutral Na atom because it is a cation.
2. S vs. S2-: The S2- anion will have a larger radius than the neutral S atom because it is an anion.
3. I vs. I-: The I- anion will have a larger radius than the neutral I atom because it is an anion.
4. Al vs. Al3+: The Al3+ cation will have a smaller radius than the neutral Al atom because it is a cation.