2. Dalton’s Atomic
Model (1803)
- First atomic model
- Developed by John Dalton
- He believed that all matter
was composed of very tiny
particles called atoms.
- He based on the notion put
forward by Democritus and
Leucippus
- Dalton’s atomic model was
solid sphere only because
the subatomic particles
were yet to be discovered.
3. Thomson’s
Plum-Pudding
Model (1904)
- Developed by J.J. Thomson
- It resembled a cup of pudding
with bits and pieces of plum
representing the electrons
- The model was composed of
the negatively-charged
particles floating in a “soup” of
positively-charged particles.
- This model prompted other
scientists to speculate on the
arrangement of electrons
inside the atom.
4. Rutherford’s
Nuclear Atomic
Model (1911)
- Discovered by Ernest
Rutherford
- The successful of the gold foil
experiment led to the discovery
of the nucleus and protons,
calling for a new design of the
atomic model.
- This model shows that the
atom is mostly empty space,
with electrons orbiting the
positively-charged nucleus in a
fixed determinable motion.
5. Bohr’s Planetary
Atomic Model
(1913)
- Discovered by Niels Bohr
- He discovered that electrons
moved around the nucleus in
a particular way.
- He concluded that this
particles orbited the nucleus
in special stationary orbits at
different energy levels.
- The electrons transfer to an
outer orbit when they gain
energy and move down to an
inner orbit when they release
energy.
6. Schrodinger’s
Quantum
Mechanical/Electron
Cloud Model (1962)
- Discovered by Erwin
Schrodinger an Austrian
Scientist.
- He advanced Niels Bohr’s
design by pointing out that
electrons form a cloud around
the nucleus, as opposed to
merely moving in circular,
determinable paths.
- He proposed the idea that the
denser the electron cloud, the
easier it is to locate an
electron.
7. ELECTRONS
SHELLS
AND
ORBITALS
Electron orbitals - are regional
spaces where electrons stay,
and it is difficult to determine
the precise location of an
electron in these spaces.
Electron shells - correspond to
different levels of energy,
which depend on the
allowable number of electrons
in them.
