Question

in the series shown below, which of the following has the most unpaired electrons? select the single best answer.
○ p
○ p²⁻
○ p³⁻
○ p⁻

Explanation:

Step1: Determine electron configuration of P

Phosphorus (P) has an atomic number of 15. Its electron configuration is $1s^2 2s^2 2p^6 3s^2 3p^3$. In the 3p subshell, there are 3 unpaired electrons (Hund's rule: electrons fill orbitals singly first).

Step2: Determine electron configuration of \( P^- \)

\( P^- \) has 16 electrons. Electron configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^4 \). In the 3p subshell, there are 2 unpaired electrons (one orbital has a pair, two have single electrons).

Step3: Determine electron configuration of \( P^{2-} \)

\( P^{2-} \) has 17 electrons. Electron configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^5 \). In the 3p subshell, there is 1 unpaired electron (four orbitals have pairs, one has a single electron).

Step4: Determine electron configuration of \( P^{3-} \)

\( P^{3-} \) has 18 electrons. Electron configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 \). All electrons are paired (noble gas configuration, like Ar), so 0 unpaired electrons.

Answer:

P (with 3 unpaired electrons)