The listed contributions are some of the concepts that were developed in the history of the atomic theory. Arrange them in order from oldest to most recent.

Answer 1

History is certainly a fascinating topic especially when it intersects with other fascinating topics like Chemistry! The history of the atomic theory has been debated. Evidence shows most support for the following:

(1) The word, "atomus" coined by well known Greek philosopher, Democritus. ~450 Before Christ (BC)

(2) John Dalton with Dalton's atomic theory (atoms, different atoms in different elements, conservation of atoms, constant atomic mass ratios) ~1803.

(3) Michael Faraday. Atomic structure related to electricity. ~ 1839.

(4) J. J. Thomson. atoms have negatively charged particles called electrons with a charge-to-mass ratio of approximately: 1.76x10⁸ C/g. ~1896. Thomson is also notably responsible for the plum pudding model regarding how e- are dispersed across a uniform positive charge.

(5) Robert Milikan. determined charge of electrons using oil droplets. Electrons charge: 1.60x10^-19C. electron's mass: 9.11x10^-28g. ~1909.

(6) Ernest Rutherford: contrasted Thomson's pudding model by proposing Rutherford' Nuclear theory asserting that positive charges are concentrated in the center of an atom in a structure called a nucleus, shown in his famous Gold Foil (alpha particle emission) experiment, also noting that most of an atom is actually empty space. ~1909.

(7) Henry Moseley: atomicn umber (# of protons) ~1910.

(8) Niels Bohr came up with the Bohr model, showing how electrons orbit the nucleus, basing it off of Hydrogen atom being the simplest model, claiming and determining that the energy of electrons is quantized. ~1911.

(9) Louis de Broglie & Schrodinger came up with wave mechanical model, saying electrons occupy orbitals surrounding the positively charged mass in the center, and that electrons can act like BOTH particles AND waves (just like light / photons). They determined orbitals to be nothing like proper uniform orbits and rather were just areas of probability density containing certain percentage frequencies of electron probability occurring in the electron cloud space. ~1924.