[Ar] in writing electron configurations

[bree_wray_14a]

Hi, today in class Dr. Lavelle was discussing how to write some e- structures of atoms and I noticed for examples like Sc, he wrote out the configuration with [Ar] in front. I do not understand why he did this.

[Praveena Ratnavel - 1A]

The "shortcut" to writing out electron configurations is to start with the noble gas before the element - for Sc, Ar is the noble gas before. From there, we can write the rest of the electron configuration. I think the point of it is to only specify the valence electrons because we can assume that the inner shells are filled.

[Ella_hou]

hi,
i think he put [Ar] as a shortcut. instead of writing the whole list of electron configuration for Sc which would be long (1s2 2s2 2p6 3s2 3p6 3d1 4s2) ,we know that Sc has to equal everything that the electron configuration of Ar is PLUS 3d^14s^2. In the end, what he's doing is putting the core value first (argon) and adding the remaining valence electrons for Snapchat. Hopes this helps.

[Kassidy Patron 1L]

Hi! He did this instead of writing out all the inner shell/orbitals. By writing [Ar], he was basically saying all the electrons in orbitals for argon, then followed with the other electrons leftover. For example, if he was writing the electron configuration for titanium, he would only have to write out the configuration for the 4 remaining electrons (the # of electrons in argon is 18, the # of electrons in titanium is 4). You can do this with other elements too, not just argon, so you can focus on writing out the valence electrons instead of writing everything out.

[Adithi Ayyala 2G]

As others already stated, this syntax is simply showing an electron configuration shortcut, where one can start at the nearest noble gas (here, it is Argon), and then continue writing electron configurations from there. This was a really nice video that explains configuration as well.

https://www.youtube.com/watch?v=NIwcDnFjj98

[Rose Arcallana 2B]

In basic terms, [Ar] is a shorthand so we don't have to write the electron configuration for all of the previous blocks. You typically do these with noble gasses considering they have all of the electron shells filled, so it would be redundant to do write it out again. :)