Which of the following is the correct electron configuration for Ru³⁺?

• A. [Kr] 4d^5 5s^1
• B. [Kr] 4d^6
• C. [Kr] 4d^7
• D. [Kr] 4d^4 5s^2

Answer: (B)

Verified step by step guidance

1. Identify the atomic number of ruthenium (Ru), which is 44. This means a neutral Ru atom has 44 electrons.
2. Write the electron configuration for a neutral Ru atom. Start with the nearest noble gas, krypton (Kr), which accounts for 36 electrons: [Kr] 4d^7 5s^1.
3. Determine the electron configuration for Ru³⁺ by removing three electrons from the neutral Ru configuration. Electrons are removed first from the outermost shell, which is the 5s orbital in this case.
4. Remove the one electron from the 5s orbital: [Kr] 4d^7.
5. Remove two more electrons from the 4d orbital to account for the 3+ charge: [Kr] 4d^5. This is the electron configuration for Ru³⁺.