Chronological timeline of the development of the atomic theories until the most
recent discoveries at the atomic level.
Scientist/s Name of Main
the Description contribut
atomic of the ion or
model/ model/theo focal
theories ries concept
(Year)
Dalton’s John Dalton Introducti
1. John Atomic proposed the on of
Dalton Theory atomic atoms of
(1803) theory in the simple
1803, stating elements
that all are alike
matter is in mass
composed of and size.
atoms,
which are
indivisible
and
indestructibl
e particles.
2. J.J. Plum According to Discovery
Thomso Pudding this model, of an
n Model the atom electron
(1897) consists of a and the
positively subatomic
charged particles
“pudding” that can
with be found
negatively within
charged atoms of
electrons all
embedded elements.
within it.
3. Ernest Rutherfor Ernest Discovery
Rutherfo d’s Gold Rutherford of the
rd Foil conducted atomic
Experime the famous nucleus
nt gold foil and the
Nuclear experiment concept of
Model in 1911, a nuclear
(1911) which led to model of
the the atom .
discovery of
the nucleus
of an atom.
He proposed
that atoms
have a
small, dense,
positively
charged
nucleus at
their center,
with
electrons
orbiting
around it.
4. Niels Bohr This model Introducti
Bohr Atomic introduced on of the
Model energy concept of
(1913) levels or quantized
shells for energy
electrons to levels in
occupy atom that
around the explained
nucleus of how
an atom. electrons
can exist
in stable
orbits
without
emitting
energy.
5. Erwin Quantum Erwin Developm
Schrödi Mechanic Schrödinger ent of
nger al Model developed a quantum
(1926) mathematica mechanics
l model and the
known as wave
quantum function
mechanics descriptio
or quantum n of the
mechanical atom that
model in describes
1926 to the
describe probability
electron that an
behavior electron
within atoms can be
more found in a
accurately given
than earlier region of
model space at a
given time
or where
it might
be.
6. James Discovery He Identificati
Chadwic of the discovered on of the
k Neutron neutron, neutron as
(1932) which is a a
neutral fundamen
particle tal
present in componen
the nucleus t of the
of an atom atomic
along with nucleus.
the protons.
