Atoms have quantum numbers that are directly analogous to the electronic quantum numbers. The problem with this idea is that the angular momenta of the various electrons are not necessarily pointing in the same direction. If they were revolving opposite to each other, you would subtract them. If you prefer to have a formula, you can use this:. The possible combinations are 2, 1, 0. We have not done a three electron case yet, but they are not hard. Find all the combinations for a single pair first, and then factor in the third electron.
If you draw a picture of the possible ways that two electrons can arrange their spins, you get something like this:. The three spin axes of an electron share a Heisenberg Uncertainty Principle. The same is true for all other combinations of x, y and z. This causes the x and y orientations of the electrons to become smeared out across all possible values:. Atomic term symbols contain two pieces of information.
Note that while the notation is similar, L does NOT say anything about what types of orbitals the electrons are in. The multiplicity is indicated by appending a number to the upper left of the symbol. An example of a forbidden electronic transition upwards of one unpaired electron to an empty orbital:. DeltaS is still 0 because it's the same electron transitioning as before, just towards a different orbital. What are they used for? It helps to know this, but you don't have to know this like the back of your hand unless you are taking Physical Chemistry.
Alright, so let's apply the selection rules themselves. I gave examples already, so let's work off of the allowed transition example and change it a little bit. The values for L , S , and J are pretty similar. You can see lines on the diagram going from the 3s orbital to two 3p orbital destinations.
That indicates either an excitation from the 3s to the 3p or a relaxation from the 3p to the 3s. These two lines are marked Lastly, an easy way to remember what transitions are allowed is to note that electronic transitions on energy level diagrams are diagonal, and involves adjacent columns. What electron configuration represents an atom in the excited state?
Chemistry Electron Configuration Electron Configuration. Jan 14, Predict the color of the flame for a substance called strontium sulfate. Explain your reasoning. Make a prediction: Why does the substance only glow when heated? What do you think is happening inside the atom?
The metal. Copper nitrate and potassium nitrate turned different colors even though they both had nitrate in them. Making Sense Qs: Did the metal or the non-metal seem to cause the color change? What is your reasoning? An electron jumped to an outer shell. Yes, 11 electrons. No, an electron has jumped up to the 4th shell into the p subshell.
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