What is the electron configuration [Ar]3d4 for Mn3+? a) [Ar]4s23d7 b) [Ar]4s13d5 c) [Ar]4s2342 d) [Ar]3d3
The Correct Answer and Explanation is:
The correct electron configuration for Mn3+\text{Mn}^{3+}Mn3+ is [Ar] 3d⁴.
Let’s break it down:
- Manganese (Mn) has an atomic number of 25, which means its neutral atom configuration is:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s².
- The electron configuration of Mn in its ground state would be: [Ar] 3d⁵ 4s².
- Mn³+ means that the manganese ion has lost three electrons. When an atom ionizes to form a positive ion, the electrons are typically lost from the outermost shell first. In this case, the 4s electrons are removed first, followed by the 3d electrons:
- Start with the neutral configuration: [Ar] 3d⁵ 4s².
- Remove two electrons from the 4s orbital: [Ar] 3d⁵.
- Remove one more electron from the 3d orbital: [Ar] 3d⁴.
Therefore, the electron configuration for Mn³+ is [Ar] 3d⁴.
Explanation:
- 4s electrons are removed before the 3d electrons because the 4s orbital is higher in energy.
- After the removal of three electrons, the remaining configuration for the ion has a total of 22 electrons, which matches the expected number for Mn³+ (the neutral Mn atom has 25 electrons).
Now, examining the choices:
- a) [Ar] 4s² 3d⁷: This is the electron configuration for a neutral Mn atom, not the Mn3+\text{Mn}^{3+}Mn3+ ion.
- b) [Ar] 4s¹ 3d⁵: This could be the configuration of Mn²+, but it’s not correct for Mn³+.
- c) [Ar] 4s² 3d⁴: Incorrect, as the 4s orbital is fully occupied before the 3d orbital.
- d) [Ar] 3d³: This would correspond to Mn4+\text{Mn}^{4+}Mn4+, not Mn3+\text{Mn}^{3+}Mn3+.
Thus, [Ar] 3d⁴ is the correct electron configuration for Mn3+\text{Mn}^{3+}Mn3+.
