Which of the following elements has the largest number of unpaired electrons in the ground state?
A) K
B) V
C) S
D) Si
E) Cl

Question

Quizplus · Accepted Answer

To determine the number of unpaired electrons, we need to find the electron configuration for each element. 
A) K - [Ar] 4s1
B) V - [Ar] 3d3 4s2
C) S - [Ne] 3s2 3p4
D) Si - [Ne] 3s2 3p2
E) Cl - [Ne] 3s2 3p5

To find the number of unpaired electrons, we look at the valence shell, specifically the outermost subshell with electrons. 
A) K has one valence electron in the 4s subshell, so one unpaired electron. 
B) V has five valence electrons - three in the 3d subshell and two in the 4s subshell. In the ground state, one of the 3d electrons is unpaired, so one unpaired electron. 
C) S has six valence electrons, four in the 3p subshell and two in the 3s subshell. All of these electrons are paired, so zero unpaired electrons. 
D) Si has four valence electrons, two in the 3p subshell and two in the 3s subshell. All of these electrons are paired, so zero unpaired electrons. 
E) Cl has seven valence electrons, five in the 3p subshell and two in the 3s subshell. One of the 3p electrons is unpaired, so one unpaired electron.

Therefore, the answer is B) V, since it has one unpaired electron in the ground state.

Which of the Following Elements Has the Largest Number of Unpaired