Atomic Models and Electron Distribution

Core concept

For example, the innermost K shell (n=1) can hold a maximum of 2 electrons, the L shell (n=2) can hold up to 8, and the M shell (n=3) can hold up to 18 — though shells generally fill from the innermost outward before electrons occupy the next shell. This electron arrangement (also called electronic configuration) determines an element's chemical behaviour, particularly how many electrons are in its outermost shell, which governs how readily it forms bonds with other atoms.