Yahoo Answers is shutting down on 4 May 2021 (Eastern Time) and the Yahoo Answers website is now in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
How come some elements fit up to 8 electrons in their 3rd shell and others can fit up to 18?
Eg. Calcium fits 8 electrons in the 3rd shell, 2 in 4th.
Copper fits 18 electrons in 3rd shell, 1 in 4th.
Also, why would nickel have 16 electrons in 3rd shell, 2 in 4th when it can have 18 electrons in 3rd shell and be stable?
1 Answer
- 1 decade agoFavourite answer
electrons go into the lowest energy level available to them. It just happens that after putting 8 electrons in the 3rd shell, it takes less energy to start putting electrons in the 4th shell. That's why calcium has only 8 electrons in its 3rd shell and 2 in its 4th shell.
After putting 2 electrons in the 4th shell it takes less energy to put them in the 3rd shell again. So any atom that already has 2 4th shell electrons, like copper, will get more electrons in its 3rd shell.
Nickel has 16 electrons in its 3rd shell and 2 in its 4th shell because that is the lowest energy configuration.
