Which of the following is the correct condensed electron configuration for the atom or ion indicated?
a) The electron configuration of Ba2+ is [Xe].
b) The electron configuration of In3+ is [Kr]5s24d8.
c) The electron configuration of Co2+ is [Ar]4s23d5.
d) The electron configuration of p3-is (Ne]3s?
e) The electron configuration of s2 is [Ne]3s23p2.
The Correct Answer and Explanation is :
The correct electron configuration for each atom or ion is based on the principle that electrons fill orbitals in order of increasing energy levels, which is described by the Aufbau principle. The electron configuration takes into account the element’s atomic number, and for ions, the loss or gain of electrons is accounted for.
Let’s review each option:
a) The electron configuration of Ba²⁺ is [Xe].
- Correct. Barium (Ba) has an atomic number of 56, so its neutral electron configuration is [Xe] 6s². When it forms the Ba²⁺ ion, it loses two electrons, typically from the 6s orbital. After the loss of these two electrons, the electron configuration becomes [Xe], which is the correct configuration for Ba²⁺.
b) The electron configuration of In³⁺ is [Kr] 5s² 4d⁸.
- Incorrect. Indium (In) has an atomic number of 49, and its neutral electron configuration is [Kr] 5s² 4d¹⁰ 5p¹. When it forms the In³⁺ ion, it loses three electrons. The first two electrons are removed from the 5p orbital, and the third electron is removed from the 5s orbital. The correct electron configuration for In³⁺ is [Kr] 4d¹⁰, not [Kr] 5s² 4d⁸.
c) The electron configuration of Co²⁺ is [Ar] 4s² 3d⁵.
- Incorrect. Cobalt (Co) has an atomic number of 27, so its neutral electron configuration is [Ar] 4s² 3d⁷. When Co forms the Co²⁺ ion, it loses two electrons, which are typically removed from the 4s orbital. Therefore, the correct electron configuration for Co²⁺ is [Ar] 3d⁷, not [Ar] 4s² 3d⁵.
d) The electron configuration of P³⁻ is [Ne] 3s².
- Incorrect. Phosphorus (P) has an atomic number of 15, so its neutral electron configuration is [Ne] 3s² 3p³. When it forms the P³⁻ ion, it gains three electrons, filling the 3p orbital. The correct electron configuration for P³⁻ is [Ne] 3s² 3p⁶, not [Ne] 3s².
e) The electron configuration of Si²⁺ is [Ne] 3s² 3p².
- Incorrect. Silicon (Si) has an atomic number of 14, and its neutral electron configuration is [Ne] 3s² 3p². When it forms the Si²⁺ ion, it loses two electrons, which are typically removed from the 3p orbital. Therefore, the correct electron configuration for Si²⁺ is [Ne] 3s².
Conclusion:
The correct answer is (a): The electron configuration of Ba²⁺ is [Xe].