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Writing Electron Configurations

Posted: Sun Oct 20, 2019 11:25 am
by Frederick Keith_4C
My high school chemistry class was really bad, so we never wrote any electron configurations and I've been a little confused. I understand that when writing them you should write in order from lowest to highest energy, but I don't understand the short hand configurations.
For example, Calcium was written as [Ar] 4s^2 and Indisum was written as [Kr] 4d^10 5s^2 5p^1
What are those elements in brackets there for and why did we choose them when writing the electron configurations?

Re: Writing Electron Configurations

Posted: Sun Oct 20, 2019 11:32 am
by Izzie Capra 2E
You choose these elements because they are the Noble Gases (column 18). This means their outer electron shells are full with electrons (they fulfill max capacity for the outer most shell), so you can use them to substitute. Instead of writing out the initial sub-shells each time, you can just pick the nearest noble gas for the shorthand and continue with the orbitals past that. They have the full configuration you would already be writing. Basically, pick the closest noble gas with less protons/electrons that you are wanting to write an electron configuration for, and then continue filling electrons in the sub shells.

Re: Writing Electron Configurations

Posted: Sun Oct 20, 2019 11:35 am
by rabiasumar2E
We use those elements because they are noble gasses and aren't reactive, meaning their configuration is complete. 'He' would be 1s2 and 'Ne' would end with 2p6. We use them to help with the configurations of other elements that are further down the periodic table mostly for convenience so we don't have to write all of it. We only use the noble gasses because knowing their configuration is simple. So if you were looking to the write the configuration of the element 'Cs', you would use the noble gas that comes right before it to help you write its configuration. In this case it would be 'Xe'. I hope this helps.

Re: Writing Electron Configurations

Posted: Sun Oct 20, 2019 11:47 am
by 305416361
So as mentioned in the previous comments, those are noble gases that are unreactive and have full valence electron shells. Essentially, think of it as substituting a variable for the configuration up until that element, the same way we substitute h for Planck's constant and c for the speed of light.