The electronic structure of an atomAll elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. is a description of how the electronSubatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. are arranged. It can be shown as numbers or as a diagram.
Take lithium for example. The diagram shows each shell as a circle around the nucleusThe central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei., with each electron represented by a dot. The electronic structure for lithium is written as 2.1 (showing that lithium atoms have three electrons, two in the first shell and one in the second shell).