An electron is in one of the 3d orbitals. Give the possible values of n, l and m_l for this electron. 

For 3d orbital. The principle quantum number is n=3.
(azimuthal quantum number) l = 2.
For the (magnetic quantum number m_l) that is given by the rule such as (2(l) +1) = (2 x2 +1) =5. Thus, the possible value of m_l =  -2, -1, 0, +1 +2.