The electron configuration of a Cr3+ ion is: A. [Ar]3d3 B. [Ar]4s13d2 C. [Ar]3d3 D. [Ar]4s13d5 E. [Ar]4s23d4
The Correct Answer and Explanation is:
The correct electron configuration for a Cr³⁺ ion is A. [Ar] 3d³.
Here’s why:
- Chromium’s Neutral Atom Configuration: Chromium (Cr) has an atomic number of 24. In its neutral state, the electron configuration is: Cr:1s22s22p63s23p63d54s1\text{Cr:} 1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1Cr:1s22s22p63s23p63d54s1 This configuration shows that chromium has 6 electrons in its 3d subshell and 1 electron in its 4s subshell. The reason for this arrangement is due to the energy stability associated with half-filled d orbitals.
- Formation of Cr³⁺: When chromium loses three electrons to form a Cr³⁺ ion, these electrons are typically removed first from the 4s orbital and then from the 3d orbitals. This is because the 4s orbital is higher in energy than the 3d orbital once the atom has already started to ionize. So, in Cr³⁺:
- The two 4s electrons are removed first.
- One electron is also removed from the 3d orbitals, leaving three electrons in the 3d subshell.
- Electron Configuration for Cr³⁺: After losing three electrons, the configuration for Cr³⁺ becomes: Cr³⁺:[Ar]3d3\text{Cr³⁺:} [Ar] 3d^3Cr³⁺:[Ar]3d3 This shows that the Cr³⁺ ion has the same electron configuration as the noble gas Argon (Ar), followed by three electrons in the 3d subshell.
- Conclusion: Thus, the correct answer is A. [Ar] 3d³. This electron configuration reflects the removal of three electrons from the neutral chromium atom, resulting in the Cr³⁺ ion with a 3d³ electron configuration.
