Question

In which of the following species, the ratio of s-electrons to p-electrons is the same?

• A. \( K^+, Cr^{3+} \)
• B. \( Zn, Fe^{2+} \)
• C. \( Zn, Cr^{3+} \)
• D. \( Na^+, K^+ \)

Hint:

Count s-electrons and p-electrons from the electron configuration.
- Find the ratio \( \frac{\text{s-electrons}}{\text{p-electrons}} \) and compare for each species.

Answer 1

The Correct Option is A

To determine the species where the ratio of s-electrons to p-electrons is the same, we analyze their electronic configurations. 1. Electronic Configuration of \( K^+ \): - Potassium (K) has an atomic number of 19. - Neutral \( K \) configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 \). - For \( K^+ \) (after losing one electron): \[ 1s^2 2s^2 2p^6 3s^2 3p^6 \] - Number of s-electrons = \( 2 + 2 + 2 = 6 \). - Number of p-electrons = \( 6 + 6 = 12 \). - Ratio \( = \frac{6}{12} = 1:2 \). 2. Electronic Configuration of \( Cr^{3+} \): - Chromium (Cr) has an atomic number of 24. - Neutral \( Cr \) configuration: \( [Ar] 3d^5 4s^1 \). - For \( Cr^{3+} \) (losing 3 electrons from \( 4s \) and \( 3d \)): \[ 1s^2 2s^2 2p^6 3s^2 3p^6 3d^3 \] - Number of s-electrons = \( 2 + 2 + 2 = 6 \). - Number of p-electrons = \( 6 + 6 = 12 \). - Ratio \( = \frac{6}{12} = 1:2 \). Since both \( K^+ \) and \( Cr^{3+} \) have the same ratio of s-electrons to p-electrons, they satisfy the condition. Thus, the correct answer is \(\boxed{K^+, Cr^{3+}}\).