Sorry for the delay! My internet is a bit bad.
P is the third sublevel. Each sublevel (the angular momentum quantum number), has its own number:
s = 1, p =3, d = 5, f = 7
The number of electrons for each is:
s-2
p-6
d-10
f-14
It's easier to just memorize these numbers, but the equation for determining the sublevel number is 2n (n = the principal quantum number). The principal quantum number is based on the period the element is in.
