Electron Cloud Definition

An electron cloud is ​the region of negative charge surrounding an atomic nucleus that is associated with an atomic orbital. It is defined mathematically, describing a region with a high probability of containing electrons.

The phrase "electron cloud" first came into use around 1925, when Erwin Schrödinger and Werner Heisenberg were seeking for a way to describe the uncertainty of the position of electrons in an atom.

Electron Cloud Model

The electron cloud model differs from the more simplistic Bohr model, in which electrons orbit the nucleus in much the same way as planets orbit the sun. In the cloud model, there are regions where an electron may likely be found, but it's theoretically possible for it to be located anywhere, including inside the nucleus.

Chemists use the electron cloud model to map out the atomic orbitals for electrons; these probability maps are not all spherical. Their shapes help predict the trends seen in the periodic table.