Atomic Models throughout history
Models to represent the
of the atom have changed over time.
was an
ancient Greek philosopher who was born in 460BC. He described matter as being made up of indivisibles
(
). This is where the name
came from. In
, atomis
means uncuttable. The ancient Greeks adopted the belief that all matter is made up of Earth, Water,
Fire and Air. Ideas about atoms and their structure didn’t change much for almost
In 1808, an English chemist, John
made up of
years.
described matter. He believed matter is
, indivisible (unable to be divided ….NOT invisible) particles
which he calls atoms. Joseph J Thomson, an English
, described atoms like a
plum pudding. The description was known as the plum
model. In this model atoms
were presented as having a heavy positive pudding with the light negatively charged
embedded in it.
The discovery of radioactivity allowed scientists to examine atoms in
Rutherford used radioactive
ways. Ernest
to find out that atoms had a tiny, very dense,
positively charged nucleus with electrons
atoms contained mainly
the nucleus. He concluded that
space. The Danish physicist, Niels Bohr improved on
Rutherford’s model in
. Bohr’s model has electrons in orbits with definite
and amounts of energy. James Chadwick discovered and identified the
. The neutron
is a neutral particle found in the nucleus.
In 1932, a new atomic model was developed. It was developed using
ideas about
atoms and the work of several new scientists. The model indicated that most of an atom’s mass is in the
.
and neutrons are found in the nucleus. The
electrons can be found in very definite areas around the nucleus but are constantly
.
The Standard Model is the commonly used atomic model in modern science. It is based on the previous
model but has more
arrangements of electrons around the atoms.
Word List……
Previous, 2000, new, solid, neutron, complex, electrons, Democritus,
pudding, atom, Protons, Greek, orbiting, empty, Dalton, structure,
atomis, 1913, physicist, particles, nucleus, positions, moving.