Which noble gas has the same electron configuration as the ion Cl^-?

• A. Xe
• B. Kr
• C. Ar
• D. Ne

Answer: (C)

Verified step by step guidance

1. Identify the electron configuration of the neutral chlorine (Cl) atom. Chlorine has an atomic number of 17, so it has 17 electrons.
2. Determine the electron configuration of the chloride ion (Cl⁻). Since it has gained one electron, it now has 18 electrons.
3. Recall that the electron configuration of an ion with 18 electrons is the same as the noble gas with atomic number 18, which is argon (Ar).
4. Write the electron configuration for Ar to confirm it matches Cl⁻: \$1s^2 2s^2 2p^6 3s^2 3p^6$.
5. Compare the electron configurations of the given noble gases (Xe, Kr, Ne) to see which matches Cl⁻. Argon (Ar) matches exactly.