# What do we mean by curly braces in an atomic configuration?

What do the '{ mean in atomic configurations e.g:

 1s(2)2s(1)2p(2){3P}3p(1)
1s(2)2s(2)2p(3){4S}3p(1)
`
• By "we" you likely mean the authors of the text where you found this. What do they say about their notation? – my2cts Feb 23 at 9:24
• All I know is that these are some excited states of Oxygen ions. I am assuming this is some form of standard representation but cannot find any explanation which is why I am asking :) – wander95 Feb 23 at 23:07