And the number of subshells. This letter N depends on the principal quantum number, and it's given by the following equation l equals n equals one. In other words, if we know that our principal quantum number in which our electron is located is n equals four, then our subshell is n minus one So four minus one L equals three. And so let's look at some examples of our subshells. S is a subshell, P is a subshell, D is a subshell, s is a subshell, and so on. Now, these S and P and D are the most familiar ones.