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 px, py and pz; For e.g., 2px, 2py and 2pz.
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 2px, 2py and 2pz, as they are symmetrical about x, y and z-axes respectively. That is, 2pxorbital has two lobes symmetrical around x-axis and 2py orbital has two lobes symmetrical around y-axis while the lobes of 2pz 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 2pz orbital, the nodal plane (in XY plane) is shown in below figure.
fig 1.4 - (b) Nodal plane in 2pz orbital2px and 2py 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.