The angular momentum quantum number of an electron in a d orbital is equal to?

##l=2##

The angular momentum quantum number, ##l##, is used to denote the subshell in which a given electron resides in an atom.

The value of the angular momentum quantum number depends on the value of the principal quantum number, ##n##, as given by

##l = {0, 1, 2, ..., n-1}##

Now, in order for an electron to be located in a ##d## orbital, it must be located in the ##d## subshell. The angular momentum quantum number designates

• ##l = 0 ->## the s subshell
• ##l=1 ->## the p subshell
• ##l=2 ->## the d subshell
• ##l=3 ->## the f subshell

In your case, all the electrons located in a ##d## orbital will share the same value of the angular momentum quantum number, i.e. ##l=2##.