Electron Configuration

Electron Configurations

• Electron configurations show the distribution of all electrons in an atom

• Each component consists of:

  • A number denoting the shell

  • A letter denoting the type of subshell

  • A superscript denoting the number of electrons in those orbitals.

Aufbau Principle

Electrons are added one at a time to the lowest energy orbitals available until all the electrons of the atoms have been accounted for.

Pauli Exclusion Principle

An orbital can hold a maximum of two electrons. To occupy the same orbital, two electrons must spin in the opposite direction. 

Hund's Rule

If two or more orbitals of equal energy are available, electrons will occupy them singly before filling orbitals in pairs.

Energies of Orbitals

• Notice that some sublevels on a given n level may have less energy than sublevels on a lower n level.  

• Ex: The energy of 4s is less than the energy of 3d.

Electron Configuration - Ground State

• All of the superscript numbers add up to the total number of electrons.

• Electron configurations are always written based on the energy level of the subshell

Shorthand Electron Configuration

Starts with the symbol of the noble gas in the previous period, followed by the rest of the electron configuration for the element in question.