Solutions to Web Experiment: Contour Plots for Atomic Orbitals
Web Experiment: Contour Plots for Atomic Orbitals
Answers to Questions
- To examine the effect of the quantum number n on the size and shape of the electron density cloud, we will construct the contour plots for the 2p, 3p, and 4p atomic orbitals. These atomic orbitals have the same l value of 1 but different n values. The effective nuclear charge, Zeff, for each plot will be set at 6.6.
The size of the electron density cloud increases with an increase in the value of n. The value of n does not affect the shape of the cloud.
- To examine the effect of the quantum number l on the size and shape of the electron density cloud, we will construct the contour plots for the 3p and 3d atomic orbitals. These atomic orbitals have the same n value of 3 but different l values. The effective nuclear charge, Zeff, for each plot will be set at 6.0.
The shape of the electron density cloud changes with a change in the value of quantum number l. The value of l does not affect the size of the cloud.
- To examine the effect of the effective nuclear charge, Zeff, on the size and shape of the electron density cloud, we will construct one contour plot for the 3p atomic orbital with a Zeff of 4.6 and a second plot for the 3p atomic orbital with a Zeff of 6.6.
When the values of n and l are held constant, the size of the electron density cloud decreases as the magnitude of Zeff increases. Zeff does not affect the shape of the electron density cloud.
- Use the
Effective Nuclear Charge Calculator to calculate the effective nuclear charge "seen" by an electron in a 2p atomic orbital for a B, C, N, O, and F atom.
Example: B
- Arrange the subshells of the electron configuration into groups as instructed.
- Enter 5 for the atomic number of boron and 2 for the two OTHER electrons in the 2s2p group that "screen" the third electron in the group. Click the 2s2p group button.
Results: The effective nuclear charge "seen" by an electron in a 2p atomic orbital
| Element |
B |
C |
N |
O |
F |
| Zeff |
2.60 |
3.25 |
3.90 |
4.55 |
5.20 |
- Does the electron density cloud for the 2p atomic orbital vary across the second period? Since the values for the quantum numbers n and l are the same for each plot and Zeff increases from boron to fluorine, we predict that the electron density clouds will decrease in size across the second period. To test this hypothesis we will construct contour plots for the 2p atomic orbital on the boron, carbon, nitrogen, oxygen, and fluorine atoms.
Indeed, the size of the contour plot for a 2p atomic orbital decreases from boron to fluorine.
- Does the electron density cloud for the valence p atomic orbital vary from one element to the next in Group 15? Both the value of the quantum number n and the value of Zeff increase as Group 15 is descended. Since increases in the values for n and Zeff have opposite effects on the size of the electron density cloud, it is difficult to predict how the size of the electron density cloud varies down the group. Hence, we will construct contour plots for a valence p atomic orbital on the nitrogen, phosphorus, and arsenic atoms.
Clearly, the size of the contour plot for the valence p atomic orbital increases down Group 15.