Shapes of p orbitals

For p-orbitals (l=1), there are three possible orientations corresponding to m = -1, 0, +1 values. This means that there are three p - orbitals in each p-subshell. These are designated as p_x, p_y and p_z; For e.g., 2p_x, 2p_y and 2p_z.

fig 1.4 - (a) Shapes of three 2p orbitals

These three orbitals are equal in energy but differ in their orientations. Each orbital consists of two lobes symmetrical about a particular axis. Depending upon the orientation of the lobes, these are designated as 2p_x, 2p_y and 2p_z, as they are symmetrical about x, y and z-axes respectively. That is, 2p_x orbital has two lobes symmetrical around x-axis and 2p_y orbital has two lobes symmetrical around y-axis while the lobes of 2p_z orbital are symmetrical around z-axis. The shape of the orbital is called dumb bell shape. The two lobes of each orbital are separated by a plane having zero electron density. This plane is known as nodal plane. For 2p_z orbital, the nodal plane (in XY plane) is shown in below figure.

fig 1.4 - (b) Nodal plane in 2p_z orbital

2p_x and 2p_y orbitals have also similar nodal planes. It should be noted that the probability of finding the electron in a particular p orbital is equal in both the lobes. The p orbitals of higher energy levels (n = 3, 4, 5… etc.) have similar shapes although their sizes are bigger.