The effective nuclear charge for the outermost electron of an oxygen atom is.

• A: 4.55
• B: 5.35
• C: 6.68
• D: None of these

The effective nuclear charge (Z_eff) for the outermost electron of an oxygen atom can be calculated using the formula:

Understanding Effective Nuclear Charge

Effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom. It accounts for the shielding effect of inner electrons.

Calculating Z_eff for Oxygen

Oxygen has 8 protons and 8 electrons. The inner electrons (2 in the 1s orbital) shield the outer electrons (6 in the 2s and 2p orbitals). The effective nuclear charge can be approximated as:

• Total protons (Z) = 8
• Shielding constant (S) ≈ 4 (due to 2 inner electrons)
• Z_eff = Z - S = 8 - 4 = 4

Choosing the Correct Answer

Based on the calculation, the effective nuclear charge for the outermost electron of an oxygen atom is approximately 4. Therefore, the correct answer is:

A: 4.55