Answer
There are 18 electron states in the $n=3$ shell.
Work Step by Step
On page 1225, the text states: "If we count all the states throughout a given shell with quantum number $n$, we find that the total number in the shell is $2n^2$"
We can find the number of electron states in the $n=3$ shell:
$2n^2 = (2)(3)^2 = 18$
There are 18 electron states in the $n=3$ shell.
