Which of the following is the approximate effective nuclear charge (Z_eff) experienced by a 2p electron in an oxygen atom?

• A. 2.00
• B. 4.45
• C. 8.00
• D. 6.00

Answer: (B)

Verified step by step guidance

1. Identify the atomic number (Z) of oxygen, which is 8, representing the total number of protons in the nucleus.
2. Determine the number of core (inner) electrons that shield the 2p electron from the full nuclear charge. For oxygen, the core electrons are those in the 1s orbital, totaling 2 electrons.
3. Estimate the shielding effect of electrons in the same shell (2s and other 2p electrons). According to Slater's rules, electrons in the same group shield less effectively, typically about 0.35 per electron.
4. Calculate the total shielding (S) by adding the contributions from core electrons and same-shell electrons. For oxygen's 2p electron, this includes 2 core electrons (each contributing 1.00) and 3 other 2p electrons (each contributing 0.35).
5. Use the formula for effective nuclear charge: \(Z_{\text{eff}} = Z - S\), where \(Z\) is the atomic number and \(S\) is the total shielding. Substitute the values to find the approximate \(Z_{\text{eff}}\) experienced by the 2p electron.