The first rule states that each electron occupies the lowest energy level possible. This is called the Aufbau principle.
{"Image DocumentName": "The first rule states that each electron occupies the lowest energy level possible. This is called the Aufbau principle.", "Image ImageDescription": "The second rule for filling orbitals is that only one electron will be put in each orbital of a sublevel until all of them are filled, and after that, they may be paired up until the sublevel is full. This is called Hund\u2019s rule.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}