history of atoms

democritus

everything in the world was made up of tiny particles; atomos

john dalton

dalton’s atomic theory; all elements are composed of individual atoms; atoms of one element are identical, atoms of different elements are different in mass, atoms of different elements can combine and form compounds

j.j. thomson

discovered the electron; created a model where atoms are positively charged with negative electrons in it; chocolate chip model; cathode ray tube

ernest rutherford

coined the term nucleus; atoms were mostly empty space and that all mass is in the nucleus; gold foil experiment

niels bohr

planetary model; electrons move in fixed energy levels and distances; dense, heavy nucleus

james chadwick

created term neutron; core contained an uncharged particle

werner heisenberg

exact location of an electron is impossible to pinpoint;