Atomic Model Timeline
John Dalton Atomic ModelEnglish chemist who proposed the Atomic Theory which
stated that all matter was composed of small indivisible
particles called atoms. These atoms possess unique
characteristics and weight for different elembets.
He also stated that three types of atoms exist: simple
(elements), compound (simple molecules), and complex
CrookesDeveloped the Crookes tube and in it produced cathode
rays for the first time. He also invented the radiometer and
BecquerelA French physicist who found that rays coming from a
uranium ore affected a photographic plate like X-rays did.
The rays were not from an external source and were more
powerful than those from a sample of pure uranium. His
experiment led to the discovery of natural radioactivity.
J.J ThompsonFirst to measure the electron. Developed the
plum-pudding model of the atom. Describes the atom as a
slightly positive sphere with small electrons inside.
Albert EinsteinProposed the quantum of light in which he states that light
behaves like a particle but also has a wave nature, giving it
a dual nature. Stated the equivalence of energy and mass
through the theory of special relativity.
Robert MillikanDiscovered the charge of an electron with his oil drop
Ernest RutherfordInferred a small, dense, positively-charged nucleus as the
result of the alpha particle scattering gold foil experiment.
Neils BohrA Danish physicist who stated that electrons could only
orbit the nucleus in successively larger orbits around the
nucleus. The outer orbits could hold more electrons. The
electrons in the outermost shell determine the properties of
the atom. He also inferred that when an electron moves from
an outer orbit to an inner orbit it emits a quantum of energy,
a photon, in the form of light