In the wave mechanical model of the atom orbitals are regions of the most probable location of

Answer is: orbitals are regions of the most probable location of electrons.

Each orbital in an atom is characterized by a unique set of values of the three quantum numbers n, l, and ml.

Magnetic quantum number (ml) specifies the orientation in space of an orbital of a given energy and shape. Magnetic quantum number divides the subshell into individual orbitals which hold the electrons, there are 2l+1 orbitals in each subshell. For example, p orbitals (and their electrons) have three orientations in spase (px, py and pz).

Principal quantum number (n) describes the size of the orbital. There are one s orbital (angular quantum number l=0), three p orbitals (angular quantum number l=1 and magnetic quantum number ml = - 1,0,+1) and five d orbitals (angular quantum number l=2 and magnetic quantum number ml = - 2,-1,0,+1,+2).