Representing Electron Configurations: Chapter 4 Lesson 3

A few simple rules, combined with the quantum numbers, will help to determine the ground-state electron configurations

Like all systems of nature, electrons in atoms tend to assume arrangements that have the lowest possible energies.

Aufbau Principle

States electron occupies the lowest-energy orbital that can receive it

Pauli Exclusion Principle

States no two electrons in the same atom can have the same set of four quantum numbers.

Hund’s Rule

States orbitals of equal energy are each occupied by 1 electron before any orbital is occupied by a second electron, and all electrons in a singly occupied orbitals must have the same spin state

Electron Configuration

Definition: The arrangement of electrons in an atom.

Orbital Notation

A representation of the electron configuration using the orbitals and arrows.

the orbital is represented by a line, with the quantum number and sublevel letter written underneath the line

the electrons are represented by an arrow

Noble-Gas Notation

A shorthand notation for writing the electron configuration

Noble Gases are in group 18

All of the noble gases, with the exception of He have an octet

Main focus is on the outer main energy level

Lewis Dot Notation

Definition: an electron-configuration notation in which only the valence electrons of an element is shown.

Indicated by dots placed around the element’s symbol