Chemistry Concepts: Energy Levels and Orbitals

By John T. Moore

Part of Chemistry For Dummies Cheat Sheet

A lot of chemistry is explained by the sharing and trading of electrons between atoms. Understanding how electrons are arranged in an atom is a building block of Chem I.

Electrons in an atom are contained in specific energy levels (1, 2, 3, and so on) that are different distances from the nucleus. The larger the number of the energy level, the farther it is from the nucleus. Electrons that are in the highest energy level are called valence electrons. Within each energy level is a volume of space where specific electrons are likely to be located. These spaces, called orbitals, are of different shapes, denoted by a letter (s, p, d, f, g). (In most cases, only the electrons contained in the s and p orbitals are considered valence electrons.) Electrons seek the lowest energy level possible.

The following electron-filling pattern indicates how the electrons fill into the energy levels. Knowing this pattern is useful in many aspects of chemistry, including predicting the bonding situation of a particular atom and in the prediction of the geometry of a covalent compound.

Electron filling pattern: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f