Some Developments of the Atom

Timeline created by science1
  • 400

    Four Fundamental Substances 400 B.C.

    Greeks proposed that all matter was composed of four fundamental substances: fire, water, earth, and air. Based on intuition Not based on experimental evidence
  • Dalton's Theory

    Each element is made up of tiny particles called atoms.
    The atoms of a given element are identical.
    Chemical compounds are formed when atoms combine with each other.
    Chemical reactions involve reorganization of the atoms. The atoms themselves are not changed in a chemical reaction.
  • J. J. Thomson

    Discovered the electron.
    All atoms have electrons.
    Developed the plum pudding model
  • Ernest Rutherford

    Metal foil experiment
    Atom has a center of concentrated positive charge
    Center contains most of the mass of the atom
    Center called the nucleus
    Nuclear Atom
    Electrons move around the nucleus at a distance relative to the nuclear radius
  • Niels Bohr

    Developed the quantum model for the hydrogen atom Electron in a hydrogen atom moves around the nucleus only in certain allowed circular orbits