Which of the following is the correct electron configuration for a fluoride ion (F-) in the ground state?

• A. 1s^2 2s^2 2p^4
• B. 1s^2 2s^2 2p^5
• C. 1s^2 2s^2 2p^3
• D. 1s^2 2s^2 2p^6

Answer: (D)

Verified step by step guidance

1. Identify the atomic number of fluorine (F), which is 9. This means a neutral fluorine atom has 9 electrons.
2. Write the electron configuration for a neutral fluorine atom by filling orbitals in order of increasing energy: 1s, 2s, then 2p. For fluorine, this is \$1s^2 2s^2 2p^5$.
3. Recognize that the fluoride ion (F-) has gained one extra electron compared to the neutral atom, so it has 10 electrons in total.
4. Add the extra electron to the next available spot in the electron configuration, which is the 2p orbital, increasing the number of electrons in 2p from 5 to 6.
5. Write the final electron configuration for the fluoride ion as \$1s^2 2s^2 2p^6$, indicating a full second shell and a stable, noble gas-like configuration.