Question

The ionic radii of the ions S2–, Cl–, and K+ are 184, 181, 138 pm respectively. Explain why these ions have different sizes even though they contain the same number of electrons.

a) Differences in electron configuration
b) Differences in nuclear charge
c) Differences in mass
d) Differences in ionization energy

Answer 1

The ionic radii of the ions S2-, Cl-, and K+ are different due to differences in electron configuration and nuclear charge.

Step-by-step explanation:

The ionic radii of the ions S2-, Cl-, and K+ are 184, 181, 138 pm respectively. The reason why these ions have different sizes even though they contain the same number of electrons is due to differences in two factors: the electron configuration and the nuclear charge.

1. Differences in electron configuration: Despite having the same number of electrons, the ions have different electron configurations, which affects their size. For example, the Cl- ion has a completely filled 3p orbital, while the K+ ion has a completely filled 3s orbital. This leads to differences in the size of the ions.
2. Differences in nuclear charge: The nuclear charge of an ion is determined by the number of protons in its nucleus. In this case, the K+ ion has the largest nuclear charge (Z = 19), while the S2- ion has the smallest nuclear charge (Z = 16). The greater the nuclear charge, the smaller the ion size.

Therefore, the differences in electron configuration and nuclear charge explain why these ions have different sizes.