HOMO (highest occupied molecular orbital)

The HOMO, or highest occupied molecular orbital, is the outermost electron-cloud in a molecule that still contains electrons. Think of it as the topmost "layer" where electrons reside before any additional electrons can jump into higher energy levels. The HOMO plays a key role in chemical reactions because it can donate electrons to other molecules, influencing how molecules interact, bond, or break apart. Its energy level also helps determine a molecule’s ability to participate in chemical processes, such as in catalysis or electrical conductivity.