UNIT 1:
An atom is made up of protons,
neutrons, and electrons, but students
did you know that before it can be
summed up as such knowledge, it has
to go through;
 a process of thinking
 discovery
 some process.
DEMOCRITUS
Around AD 143
a Greek philosopher.
Propose the idea that the
substance contains the
particles that are very
small called the
ATOM
____________
EUGEN GOLDSTEIN
 1886
 German scientist
 discovered positively
charged particles (+)
in the radiation
emanating from atoms
JOSEPH JOHN THOMSON
 1897
 British scientist
 discovered negatively
charged particles (-) in
the radiation
emanating from atoms
JOHN DALTON
 1803-1808
 British scientist
 proposed atomic
theory
“states that matter is
made of tiny, indivisible
particles called atoms”.
“The same element has the same mass,
and the atoms of the different element
have different masses.”
HANTARO NAGAOKA
1904
Japanese physicist
proposed an atomic model
like “Saturn”
the atomic center consists of
large positively charged particles
(+) and a large number of
electrons moving around.
ERNEST RUTHERFORD
1911
Physicist New Zealander
proposed the idea that atoms
consist of:
1) positively charged particles
2) a small centered nucleus
3) electrons
electrons orbit the nucleus at
different levels.
JAMES CHADWICK
1932
discovered that atomic weight
of helium is twice as heavy as
it should be.
proposed the idea that the
“atomic nucleus contained not
only positively charged
particles. But there are also
electrically neutral particles,
later called:
Neutron
_____________
Balls
Plums
Pudding
Nuclear
Protons
Experiments
Neutrons
Shells
Electrons
Nucleus
Positive
Plum pudding