Question

How many of the following elements have 1 unpaired electron in the ground state?

How many of the following elements have 1 unpaired electron in the ground state?

B, Al, S, Cl

a. 1

b. 2

c. 3

d. 4

Answers

Let's look at the configuration of each element:

Boron: 1s2,2s2,2p1 - 1 unpaired electron

Aluminum: similar to boron: 1s2,2s2,2p6,3s2,3p1 - 1 unpaired electron

Sulfur: 1s2,2s2,2p6,3s2,3px2,3py1,3pz1 - remember that a second electron

doesn't go into the same subshell with another till all the subshells have one

electron in them, so sulfur has 2 unpaired electrons in the ground state

Chlorine: 1s2,2s2,2p6,3s2,3px2,3py2,3pz1 - 1 unpaired electron

So 3 of the listed elements have 1 unpaired electron - all except sulfur

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