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Atomic Theory Song
Matter &
The Atomic Model
A Timeline of Discovery
Matter
The term matter describes all of the
physical substances around us: your
table, your body, a pencil, water,
and so forth
Defined as anything that has mass and
takes up space (has volume)
– Includes all things that can be seen,
tasted, smelled, or touched
– Does not include heat, sound, or
light
Matter is made of atoms
The Atomic Model
A Timeline of Discovery
Models are often used for things that are too small or too
large to be observed or that are too difficult to be
understood easily
In the case of atoms, scientists use large models to explain
something that is very small
Models of the atom were used to explain data or facts that
were gathered experimentally.
So, these models are also theories
Early Models of the Atom
Democritus
Greek Philosopher( 470-380B.C)
Universe was made of
empty space and tiny bits
of stuff
Called these tiny bits of
small, hard particles he
called “ atomos”
Atoms could not be divided
into smaller pieces
Early Models of the Atom
Dalton 1808
Created the first Atomic
Theory.
He viewed atoms as tiny
solid balls.
His theory had 4 statements.
Dalton’s Theory
All elements are composed of indivisible
particles.
Atoms of the same element are the same
Atoms of different elements are different.
Compounds consisted of atoms of different
elements combined together
Early Models of the Atom
JJ Thompson 1897
He was the first
scientist to show that
atoms were made of
even smaller things.
Early Models of the Atom
Thompson
Plum pudding model
Atom made of a positively
charged material with the
negatively charged
electrons scattered through
it.
JJ Thompson’s Ideas
Cathode Ray Tube Experiment
Early Models of the Atom
Rutherford 1911
Discovered protons
and nucleus
Early Models of the Atom
Rutherford
Mostly empty space
Small, positive
nucleus
Contained protons
Negative electrons
scattered around the
outside
Rutherford’s Gold Foil
Experiment
Early Models of the Atom
Bohr 1913
Electrons move in around the nucleus in specific
layers or shells
Every atom has a specific number of electron shells.
Early Models of the Atom
Chadwick 1932
Discovered the neutron
Ernst Schrödinger 1887-1961
Werner Heisenberg 1901-1976
Quantum Mechanical
Model 1926
– Electrons are in probability
zones called “orbitals”, not
orbits and the location
cannot be pinpointed
– Electrons are particles and
waves at the same time
– Developed quantum
numbers based on theories
of Einstein and Planck
Orbitals
Dmitri Mendeleev
In the late 1860s, Mendeleev began working on his great
achievement: the periodic table of the elements. By
arranging all of the 63 elements then known by their atomic
weights, he managed to organize them into groups
possessing similar properties. Where a gap existed in the
table, he predicted a new element would one day be found
and deduced its properties
Henry Moseley
1913
When atoms were arranged according to
increasing atomic number, the few problems
with Mendeleev's periodic table had disappeared.
Because of Moseley's work, the modern periodic
table is based on the atomic numbers of the
elements.
Atomic Theory
JJ
Thomson
Democratus
400 BC
1803
John
Dalton
1904
Niels
Bohr
1910
Ernest
Rutherford
1913
1926
Schroedinger
/ Heisenberg