Noble Gas Configurations

As you can imagine, electron configurations can get long and unwieldy as the number of electrons in an atom increases. The solution to that is to use a short-cut.

Let’s look at two electron configurations: Neon and Chlorine

Note, as the box indicates, that part of chlorine’s electron configuration is identical to neon’s configuration. So, it was decided that we could shortcut chlorine’s configuration by writing this:

There are a few rules that we have to follow to use this shortcut:

• The element in the brackets MUST be a noble gas - the elements in the far right column of the table

• You must use the noble gas on the row BEFORE the element or ion you are describing

• You cannot define a noble gas as itself (in other words you can’t use [Ne] for Ne.