Which of the following atoms has valence electrons that experience the greatest effective nuclear charge?

• A. C
• B. O
• C. F
• D. N

Answer: (C)

Verified step by step guidance

1. Recall that the effective nuclear charge (Z_eff) is the net positive charge experienced by valence electrons, calculated as \(Z_{eff} = Z - S\), where \(Z\) is the atomic number and \(S\) is the shielding constant representing electron repulsion.
2. Identify the atomic numbers (\(Z\)) of the given atoms: Carbon (C) has \(Z=6\), Nitrogen (N) has \(Z=7\), Oxygen (O) has \(Z=8\), and Fluorine (F) has \(Z=9\).
3. Consider that all these atoms are in the same period (row) of the periodic table, so their valence electrons are in the same principal energy level, meaning shielding by inner electrons is similar.
4. Since shielding by inner electrons is roughly constant, the effective nuclear charge increases with increasing atomic number \(Z\) because more protons pull the valence electrons more strongly.
5. Therefore, compare the atomic numbers to determine which atom's valence electrons experience the greatest \(Z_{eff}\); the atom with the highest \(Z\) (Fluorine) will have the greatest effective nuclear charge.