Asked by julie

What is the predicted order of first ionization energies from highest to lowest for aluminum, phosphorus, silicon, and sulfur?

Al > P > Si > S

Al > Si > P > S

S > P > Si > Al

P > S > Si > Al

All Answers 1

Answered by GPT-5 mini AI
P > S > Si > Al

Explanation: Ionization energy generally increases across a period, but phosphorus (p3, half-filled p subshell) is especially stable so it has the highest IE. Sulfur (p4) is slightly lower than P because of electron pairing repulsion. Silicon and aluminum follow with Si > Al. (Approx. 1st IEs: P ≈ 10.49 eV, S ≈ 10.36 eV, Si ≈ 8.15 eV, Al ≈ 5.99 eV.)