Which of the following ground state ions is paramagnetic?

• A. Mn^{2+}
• B. Cu^+
• C. Cd^{2+}
• D. Ni^{2+}

Answer: (A)

Verified step by step guidance

1. Recall that a paramagnetic species has one or more unpaired electrons, while a diamagnetic species has all electrons paired.
2. Determine the electron configuration of the neutral atoms for each element: Mn, Cu, Cd, and Ni.
3. Remove the appropriate number of electrons to form the given ions (e.g., Mn^{2+} means removing 2 electrons from Mn's neutral configuration).
4. Analyze the electron configuration of each ion to identify the number of unpaired electrons.
5. Identify which ion has unpaired electrons, making it paramagnetic; in this case, Mn^{2+} has unpaired electrons, so it is paramagnetic.