Mrs. Howell’s Grade 9 Science: Acton District High School
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1903AD 1911AD 1922AD
Beyond
The idea started around..
About 450 BC
The Greek philosopher
Empedocles
stated that matter
consists of four
elements
-earth, air, fire & water450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1903AD 1911AD 1922AD
But about…
About 400 BC
The Greek philosopher
Democritus
developed the first
atomic hypothesis.
- All matter be subdivided
only to a certain point, at
which only atoms remain.
“Atomos”- Greek word
for indivisible
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1903AD 1911AD 1922AD
Unfortunately...
About 350 BC
The Greek philosopher
Aristotle
opposed Democritus' idea
of atoms and dismissed it
as worthless and promoted
the 4 element model.
Because of Aristotle’s great
influence in the science
world, this concept about
matter lasted for more than
2000 years.
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1903AD 1911AD 1922AD
A.D. 500-1600
Arabian, Chinese and
European
Alchemists
studied matter,
experimenting with
different chemical
substances.
They devised the system
chemical symbols.
-but they still used the four
element system450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1903AD 1911AD 1922AD
A.D. 1650-1700’s
Robert Boyle
Antoine Lavoisier
Joseph Priestley
Henry Cavendish
Found that matter such as
air and water were made of
a mixture of pure
substances.
Their research promoted the
idea of matter being made of
‘elements’ and disproved the
idea of the four element
system .
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD
1897AD
1898AD
1911AD 1922AD
1808 A.D.
British scientist
John Dalton
Pictured the atom as a tiny,
indivisible sphere much
like a billiard ball.
Further developed the idea
of ‘atom particles’ in his
atomic theory .
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1855AD 1879AD
1897AD
1898AD
1911AD 1922AD
Dalton's Atomic Theory - 1808
•All elements are composed of atoms (indivisible
particles)
•All atoms of the same element are identical - in
particular they have the same mass.
•The atoms of one kind of element are different from the
atoms of all other elements - in particular the atoms of
one element have a different mass than those of other
elements.
•Atoms are indestructible and retain their identity in
chemical reactions.
• Compounds are formed by joining atoms in specific
whole number ratios.
1855 A.D.
German scientist
Heinrich Geissler
A glassblower and
inventor of the sealed glass
tubes that pumped out air
and discharged electricity
through gases.
-his invention helped lead
to the next two atom
discoveries-
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1855AD 1879AD 1897AD 1898AD 1903AD 1911AD 1922AD
1879 A.D.
British scientist
William Crookes
Discovered as the pressure
was lowered in a electric
gas discharge tube, the
negative end appeared to
emit rays, now known to be
a stream of free electrons.
This stream also could push
a tiny windmill in the tube.
Discovery of charged
particles and that they had
mass .
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1855AD 1879AD
1897AD 1898AD
1911AD 1922AD
1897 A.D.
British scientist
J.J. Thomson
Experimented on the
streams of particles using
magnets and electric
current and discovered the
pieces of atoms we know as
electrons and protons.
- Proposed the “raisin bun”
model of the atom. Positive
charged sphere with
negatively charged particles
embedded in it450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1911AD
1922AD
1896-1898 A.D.
French (Polish) scientists
Henri Becquerel
Pierre & Marie Curie
Experimented with natural
radioactivity.
- Their work and the
materials they discovered
greatly helped the next
proposed model of the
atom -
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1911AD
1922AD
1911 A.D.
New Zealand scientist
Ernest
Rutherford
Experimented with a
radiation source that
sent out alpha
particles through a
thin piece of gold foil
to a detector screen
that glowed when it
was hit.
Most particles passed
through the foil, but 1
in 8000 bounced
back!
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1911AD
1922AD
1911 A.D.
Ernest Rutherford
Proposed that if the
particles bounced back that
the atom must consist of a
tiny, dense, positive core
called a nucleus and is
surrounded by a cloud of
moving negative electrons,
and not a sphere with
embedded electrons
(JJ.Thomson’s idea).
-Discovered the second subatomic particle of the atom:
the proton (+) & new model
for the atom 450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD 1911AD
1922AD
1922 A.D.
Danish scientist
Niels Bohr
Came up with experimental
evidence proving that
electrons exist in energy
levels (shells) orbiting
around a positively charged
nucleus.
-Orbital electron energy
shells -
450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD
1911AD
1922AD
1932AD
1932 A.D.
English scientist
James Chadwick
Using alpha particles
discovered a neutral atomic
particle with a mass close to
a proton. What he
discovered was the
neutron.
-Discovered the third subatomic particle of the atom:
the neutron 450 BC 400 BC 350 BC
500-1600 AD
1650 AD Late 1700’s
1808AD 1831AD 1879AD 1897AD 1898AD
1911AD
1922AD
1932AD
History of the Atomic
Theory
(see text pg 82 through pg 85 and 91)
A. Fill in the Blank areas in this table during the
lesson or review the presentation on our class’
website.
Your task:
Work on filling out the
worksheet on the
history of the atom
table as well as
drawing the examples
of the models of the
atom on the bottom of
the sheet.
And
B. Draw the Atom Models of:
Dalton
Time
Perio
d
Scientists
Ancien
t
Greec
e
Empedocles
Ancien
t
Greec
e
Democritus
A.D.
5001600
1650
-late
1700’
Alchemists
1808
John Dalton
1879
William
Crookes
1897
J.J. Thomson
(Nobel prize
1906)
1911
Ernest Rutherford
(Nobel prize
1908)
1922
Niels Bohr
(Nobel prize
1922)
1932
James Chadwick
(Nobel prize
1935)
Atomic Model
Four element
model
What discovery they
made
Elements like Zinc,
Bithmuth, Phosphorous,
and Arsenic
Robert Boyle
Antoine Lavoisier
Joseph Priestley
Henry Cavendish
J.J. Thomson
Rutherford
Bohr
Thank you!