How many values of ml are possible for an electron with orbital quantum number l = 2?

The angular momentum quantum number is denoted by l. It gives the number of subshells and the shape of the orbital.
magnetic quantum number is denoted by ml and gives the number of degenerate orbitals in the subshell.
the values of ml for l are from -l to +l
since l = 2
type of subshell is p.
ml when l = 2 are 
-2, -1, 0 , +1 +2
altogether there are 6 different values of ml when l = 2
this means that p subshell has 6 degenerate orbitals 

You know how the first one if filled up like the objects do the same but with the other categories

Answer is to avoid experimental error