Question

The first ionization for phosphorus is $1060kJ/mol$, and that for sulfur is $1005kJ/mol$.
Which is the best explanation for this difference in first ionization energy?

• A. Sulfur has a larger nuclear charge than phosphorus.
• B. Sulfur has a larger number of inner electrons that create a greater shielding effect.
• C. Electron repulsion in the $3p^4$ in sulfur makes the electron easier to remove than the $3p^3$ electron in phosphorus.
• D. A sulfur atom is larger than a phosphorus atom.

Answer 1

The correct option is C Electron repulsion in the $3p^4$ in sulfur makes the electron easier to remove than the $3p^3$ electron in phosphorus.

Phosphorous has half filled $3p$ subshell and hence has extra paramagnetic stability, however Sulphur has $3p^4$ configuration hence one electron pair is present which results in repulsion, so removal of electron becomes easier. Thus correct option is C.