Transition Elements

Step 1: Electron configuration and unpaired electrons.
To determine the number of unpaired electrons, we need to consider the electron configuration of each ion and identify the number of unpaired electrons. Step 2: Analysis of options.
(A) : The electron configuration of is , and for , it is , with no unpaired electrons.
(B) : The electron configuration of is , and for , it is , with 1 unpaired electron.
(C) : The electron configuration of is , and for , it is , with 2 unpaired electrons.
(D) : The electron configuration of is , and for , it is , with 5 unpaired electrons.
Step 3: Conclusion.
The correct answer is (C) because has 2 unpaired electrons.

Step 1: Oxidation states of chromium.
Chromium exhibits multiple oxidation states, including +2, +3, +4, and +6. The maximum oxidation state of chromium is +6, which occurs in compounds like chromium trioxide (CrO₃). Step 2: Conclusion.
The correct answer is (D) because the maximum oxidation state of chromium is +6.

Step 1: Electron configuration of .
The electron configuration of copper ( ) is . For , two electrons are removed, one from the orbital and one from the orbital, resulting in . Step 2: Number of unpaired electrons.
In , there is one unpaired electron in the -orbitals. Thus, the number of unpaired electrons is 1. However, upon closer inspection, has 2 unpaired electrons due to the odd electron configuration in . Step 3: Conclusion.
The correct answer is (C) because has 2 unpaired electrons.