Electron configuration is a way of notating electrons in the shells of atoms. Understanding electron configuration will help us understand the nature of specific atoms and molecules as well as molecular orbital theory (MOT) later.

Here is the Open Stax image of understanding the relationship between electron configuration and location on the periodic table.

Things to remember:

• when something has a +# charge, it lacks (an) electron(s), so subtract the number (of) electron(s) from what you would normally write for that atom.
  • ex. Na: 1s²2s²2p⁶3s¹
  • ex. Na⁺: 1s²2s²2p⁶
• when something has a -# charge, it has an extra electron, so add the number (of) electrons to what you would normally write for that atom.
  • ex. P: 1s²2s²2p⁶3s²3p³
  • ex. P³⁻: 1s²2s²2p⁶3s²3p⁶
• you can use shorthand notation where you build the electron configuration from the nearest noble gas
  • ex. Na:1s²2s²2p⁶3s¹ = Na: [Ne]3s¹