Each main shell contains the same number of subshells as the main shell
number. The first main shell, or the K shell, has one subshell, as illustrated in
the diagram below.
ELECTRON DISTRIBUTION IN SUBSHELLS
The second, or L, shell contains two subshells; the third shell contains three
subshells, and so on. Beneath each subshell shown in the diagram above,
there is a numeral indicating the maximum number of electrons possible for
each subshell. Notice that the maximum total number of electrons in the
subshells of any main shell is equal to the maximum number possible for that
The maximum number of subshells within each main shell of an atom is
equal to the _______________________________ number.