M16 2py-orbital

Aim: To show the spatial probability distribution of the py-orbital

The electron density of the 2p-orbital 2p (n=2, l=1) is not spherical. Each p-orbital is concentrated along a particular axis, and consists of two parts (called lobes), one on either side of the nucleus. Since the axes of the orbitals are perpendicular to one another, there will be three identical orbitals : 2px , 2py , 2pz. On the left of illustration M16 the radial probability diagram of 2py orbital is shown. In the middle of the illustration the cross section of the electron density cloud is shown. It can be seen that the density gradually increases to a maximum and then decreases again with increasing distance from the nucleus.

 

   The diagram on the right of illustration M16 gives a representation of the shape of a 2p-orbital corresponding to the boundary surface enclosing the volume in which there is a 90% chance of finding an electron. Strictly speaking the lobes do not touch at the origin as can be clearly seen in the cross section diagram for the electron density. The form drawn here is, however, identical to that found in many text books.

Notes

Illustrations M14, M15, and M16 show the spatial probability distributions for the 1s, 2s, and 2py orbitals respectively.
It is also possible to define directional probability distributions. These are obtained by drawing vectors, originating at the centre of the nucleus, where the length of the vector is proportional to the probability of finding an electron in a given direction. This produces spheres for the 1s and 2s orbitals and dumb-bells (which do pass through the origin) for the 2p orbitals.

References:

C.E. Mortimer, ‘Chemistry’, Wadsworth Publishing
Company, Belmont, California.
J.E. Huheey, ‘Inorganic Chemistry, Principles of structure
and reactivity’, Harper International SI edition, New-
York.