In the fourth century BC the Greeks established that matter was made up of atoms. Early laboratory work were conducted in the late eighteenth century by the British physicist John Dalton, whose experiences led him to define the atom as indivisible particles that retain their chemical properties. By the late nineteenth century, among other advances, the discovery of the electron allowed to define its structure. The atom consists of protons, electrically charged positively and neutrally charged neutrons. A sheath surrounding the core of electrons, negative charge, which equals the number of protons in the nucleus. The first atomic model was unveiled by the British physicist William Thomson, who explained the stability of matter and its chemical behavior.
The Greek word "atom" means "not divisible." But throughout history it was found that consists of subatomic particles called electrons, protons and neutrons.
The hydrogen atom is the lightest element that exists, it has only one proton and one electron, and was widely used in scientific experiments.
The atoms of simple bodies unite to form molecules in compound bodies.