Which of the following best defines the effective nuclear charge (Z_{eff}) experienced by an electron in a multi-electron atom?

• A. Z_{eff} = Z + S, where Z is the atomic number and S is the shielding constant
• B. Z_{eff} = S - Z, where Z is the atomic number and S is the shielding constant
• C. Z_{eff} = Z \times S, where Z is the atomic number and S is the shielding constant
• D. Z_{eff} = Z - S, where Z is the atomic number and S is the shielding constant

Answer: (D)

Verified step by step guidance

1. Understand that the effective nuclear charge (\(Z_{eff}\)) is the net positive charge experienced by an electron in a multi-electron atom after accounting for the shielding effect of other electrons.
2. Recognize that the atomic number (\(Z\)) represents the total positive charge of the nucleus, which attracts the electrons.
3. Know that the shielding constant (\(S\)) quantifies the extent to which other electrons reduce the full nuclear charge felt by a particular electron.
4. Apply the formula for effective nuclear charge, which subtracts the shielding effect from the total nuclear charge: \(Z_{eff} = Z - S\).
5. Interpret this formula as meaning the electron experiences a reduced nuclear charge due to repulsion from other electrons, making \(Z_{eff}\) less than \(Z\).