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Hi! I was just wondering if the two exceptions that Lavelle mentioned in lecture regarding electron configuration (for Copper and Chromium) continue and carry on the same pattern going down groups 6 and 11 on the periodic table. Thanks so much!
A quick google search turned out that molybdenum has the same valence electron configuration as chromium but tungsten does not, while both silver and gold have the same valence electron configuration as copper.
Copper and Chromium are the only exceptions to the Aufbau principle because they want to have a symmetrical distribution of electrons since this would make the elements more stable. Copper wants to have its sublevel full (3d10 instead of 3d9) and Chromium wants to keep its sublevel half-filled (3d5 instead of 3d4)- in order to achieve this stability an excited electron from the 4s orbital moves to the 3d subshell. This is achievable for these two elements because the 4s and 3d subshells are close in energy and the 4s orbital has a lot of electron repulsion so it's easier for them to remove a 4s electron.
In other words, the two exceptions are for a half-filled d5 and full d10 subshells because they have lower energy. Like Angelica said, this is to make the atom more stable. These exceptions pull one electron from the s subshell (which is the subshell that holds valence electrons in this case) and put them into the d subshell to either fill it halfway so there is one electron in each orbital or to fill it all the way so that there are two electrons in each orbital.
I agree with Angelica! But in regards to the grouping, I remember Lavelle saying in class that groups in the periodic table are grouped together because of similiar properties, and so yes the groups did have more exceptions besides Chromium and Copper. But in regards to this particular test, and in general, Chromium and Copper are the main exceptions we need to know and memorize .
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