Shape of atomic orbital (s and p orbitals only)

Shape of s orbital

s orbitals are non-directional and spherically symmetrical, This means that the probability of finding the electron is same in all directions at a particular distance from the nucleus, The 1s orbital is shown in the figure 1.3.

fig 1.3 - Shapes of 1s and 2s orbitals

It is observed that density of charge cloud is maximum at the nucleus and decreases with increase in distance from the nucleus. The 2s orbital is also non-directional and spherically symmetrical. In this case, the density is maximum at the nucleus and becomes small at large distances. However, the effective volume or size of 2s is larger than 1s orbital. An important feature of 2s orbital is that there is a spherical shell within 2s orbital (region without dots) where the probability of finding the electron is practically zero, This is called a node or a nodal surface. Thus, a 2s orbital differs from 1s orbital in being larger in size and having a nodal surface. The higher s orbitals have also spherical shapes and number of nodal surfaces in s orbital for any given energy level is n - 1, where n represents energy level.

Shape of p orbital:

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_xorbital 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.