Which of the following is the correct electron configuration for the Mg^{2+} ion?

• A. 1s^2 2s^2 2p^4
• B. 1s^2 2s^2 2p^6 3s^1
• C. 1s^2 2s^2 2p^6
• D. 1s^2 2s^2 2p^6 3s^2

Answer: (C)

Verified step by step guidance

1. Step 1: Identify the atomic number of magnesium (Mg), which is 12. This means a neutral Mg atom has 12 electrons.
2. Step 2: Understand that the Mg^{2+} ion has lost 2 electrons, so it has 12 - 2 = 10 electrons.
3. Step 3: Write the electron configuration for 10 electrons, which corresponds to the electron configuration of neon (Ne), the noble gas before Mg.
4. Step 4: Recall the order of filling orbitals: 1s, 2s, 2p, 3s, etc. For 10 electrons, the configuration fills up to 2p orbitals completely.
5. Step 5: Conclude that the correct electron configuration for Mg^{2+} is \$1s^2 2s^2 2p^6$, since the 3s electrons are removed when forming the ion.