Atomic theory

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ATOMIC STRUCTURE
Scientists that changed our
view of the atom
Democritus
•Did not conduct any
experiments
•All matter is made of atoms
•Atoms are indivisible and
indestructible
John Dalton


John Dalton was
born on September
6, 1766 in Cumbria,
England.
He provided us with
the first concrete
ideas about the
atom.
John Dalton – His Experiment
John Dalton
Four points to his theory:
1.
2.
3.
4.
5.
All matter is composed of atoms that are
indestructible and indivisible
Atoms of one element are all the same; atoms of a
different element are different (Au atoms are
different from Ag atoms)
Atoms cannot be changed into different atoms by
chemical of physical changes (Pb atoms cannot be
turned into Au atoms)
All atoms are like Billiard Balls – a solid, sphere
Atoms react in whole numbers
JJ Thomson


Joseph John
Thomson was born
in Cheetham Hill, a
suburb of
Manchester on
December 18, 1856.
He is given credit for
the discovery of the
electron.
JJ Thomson – His Experiment
Cathode Ray Tube
JJ Thomson – His Experiment
JJ Thomson
3 Points to his theory
1.
2.
3.
* All gases had the
same mass: charge
ratio
* All atoms contain
small, charged
particles called
electrons
* The atom now looked
like “Plum Pudding”
Goldstein

Eugene Goldstein
was born in 1850 in
Germany.
Goldstein – His Experiment
Cathode Ray Tube
Goldstein
Major Point to his theory
He is given credit for the discovery of a positively
charged particle = Proton
The atom was still thought to resemble Plum
Pudding
Millikan

Robert Andrews
Millikan was born on
the 22nd of March,
1868, in Morrison, Ill.
(U.S.A. )
Millikan – His Experiment
Oil Drop
Experiment
Millikan
2 Points to his theory
1.
All electrons have the same mass
About 1/2000 atomic mass unit
2.
All electrons have the same charge
-1.6 x 10 -19 Coulomb
The atom was still thought to resemble Plum Pudding
Rutherford

Ernest Rutherford
was born August 30,
1871 in Nelson, New
Zealand (one of 12
children)
Rutherford – His Experiment
Rutherford
3 Points to his theory
1.
* Most alpha particle
went through = Atom is
mostly empty space
(area of electrons)
2.
* Some alpha particles
bounced straight back =
atom has a solid mass
(nucleus)
3.
* Some alpha particles
reflected = nucleus is
positively charged
New Model = Nuclear Model
Schrödinger

Erwin Schrödinger
born August 12 in
Vienna, Austria in
1887.
Schrödinger – His Experiment
Schrödinger
Major points
1.
Electrons do not follow
fixed paths
2.
They move randomly in
areas of probability
(orbitals)
3.
There are specific energies
associated with each
orbital
New Model =
Quantum Mechanical Model
Chadwick

James Chadwick
was born in
Cheshire, England,
on 20th October,
1891.
Chadwick – His Experiment
Chadwick
2 Points to his theory
1.
2.
Discovered the Neutron – Same mass
as a proton, but without a charge
Mass could be converted into energy
Model was still thought to resemble the Quantum
Mechanical Model
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