Electron Configuration and Energy Level Diagrams

Unit 4, lesson 3

Pauli exclusion principle

no two electrons can have the same set of quantum numbers
each orbital can only hold 2 electrons with opposite spins

Aufbau principle

electrons will first occupy the orbital of the lowest energy level

Hund's rule

every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied
all electrons in singly occupied orbitals have same spin

Why do we add 4s before 3d?

energy of the 4s orbital is lower than 3d
aufbau's principle states we must add electrons to lowest level

when dealing with ions

electrons are added or removed from orbital with greatest primary quantum number (n value)

what are energy level diagrams (orbital box diagrams)

illustrations that represent electron configuration of atom/ion
must apply aufbau's principle, hund's rule, and pauli's exclusion principle
boxes represent 1 orbital and can only hold 2 electrons
drawn with up and down arrows to represent spin

what are degenerate orbitals

same height, fill them one at a time