Contour Plots for Atomic Orbitals Tutorial

Tutorial for Experiment: Contour Plots for Atomic Orbitals

EXAMPLE: How do the contour plots for the 2p and 3p atomic orbitals on the silicon atom differ?

EXPERIMENT: Construct contour plots for the 2p and 3p atomic orbitals on silicon and compare them. The effective nuclear charges "seen" by the electrons in the 2p and 3p atomic orbitals are required for the plots.

PROCEDURE:

  1. Write the electron configuration for a silicon atom in its ground electronic state.



  2. Follow the instructions in the "Effective Nuclear Charge Calculator" applet and arrange the subshells into groups.



  3. Open "Effective Nuclear Charge Calculator" applet. Enter 14 for the "atomic number" of silicon and 7 for the seven OTHER electrons in the 2s2p group that "screen" the eighth electron in the group. Click the "2s2p" group button to obtain the effective nuclear charge "seen" by an electron in the 2s2p group.



  4. Next enter 3 for the three OTHER electrons in the 3s3p group that "screen" the fourth electron in the group. Click the "3s3p" group button to obtain the effective nuclear charge "seen" by an electron in the 3s3p group.



  5. Return to the "Experiment: Contour Plots for Atomic Orbitals" applet and construct the contour plot for a 2p atomic orbital on silicon. Enter 9.850 for the effective nuclear charge, Zeff, and click the button labeled "2p."



  6. To obtain the contour plot for a 3p atomic orbital on silicon, enter 4.149 for the effective nuclear charge, Zeff, and click the "3p" button.





 RESULTS and OBSERVATIONS: Both contour plots have two lobes and hence are similar in shape.



However, the size of the contour plot - the area in which there is a 99% chance of finding the electron - is much larger for the 3p atomic orbital than the 2p atomic orbital. Also the contour plot for the 3p atomic orbital has one node. A node is a point where y and hence y2 is zero. There are no nodes in the contour plot for the 2p atomic orbital.