Phosphorus and sulfur are consecutive elements in Period 3
CHEMISTRY · Single correct · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
Phosphorus and sulfur are consecutive elements in Period 3. The first-ionization energy of sulfur is slightly lower than that of phosphorus. Which of the following best explains this observation?
(a) Sulfur has a higher nuclear charge than phosphorus, so its outer electrons are more tightly held.
(b) Because sulfur is more electronegative than phosphorus, it tends to attract new electrons rather than hold its own, lowering the energy needed to remove one.
(c) Sulfur has a paired electron in a 3p orbital, and the repulsion between the paired electrons lowers the energy needed to remove one.
(d) Phosphorus experiences greater shielding by inner electrons than sulfur, reducing its effective nuclear charge and the energy required to remove an electron.