Which of the following is the correct electron configuration for the iodide ion, I⁻?

• A. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^5
• B. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^3
• C. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6
• D. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^4

Answer: (C)

Verified step by step guidance

1. Identify the element and its atomic number: Iodine (I) has an atomic number of 53, meaning a neutral iodine atom has 53 electrons.
2. Determine the electron configuration of neutral iodine by filling orbitals in order of increasing energy, following the Aufbau principle, Pauli exclusion principle, and Hund's rule.
3. Recognize that the iodide ion (I⁻) has gained one extra electron compared to neutral iodine, so it has 54 electrons in total.
4. Add this extra electron to the next available orbital in the neutral iodine configuration, which is the 5p orbital, increasing the electron count in 5p from 5 to 6.
5. Write the full electron configuration for I⁻ by including all filled orbitals up to 5p^6, ensuring the total electron count matches 54.