Question

1. how many unpaired electrons does mn²⁺ have? (hint: write the e.c.)

Explanation:

Step1: Determine Mn's atomic number

Manganese (Mn) has an atomic number of 25, so its neutral electron configuration (e.c.) is $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^5$.

Step2: Find $Mn^{2+}$ electron configuration

When Mn loses 2 electrons to form $Mn^{2+}$, it loses the 2 electrons from the 4s orbital first. So the e.c. of $Mn^{2+}$ is $1s^2 2s^2 2p^6 3s^2 3p^6 3d^5$.

Step3: Analyze unpaired electrons in 3d

The 3d subshell has 5 orbitals, and according to Hund's rule, electrons fill orbitals singly first. The $3d^5$ configuration means each of the 5 3d orbitals has one unpaired electron (since 5 electrons in 5 orbitals, each orbital gets one before pairing).

Answer:

5