Transcript John Dalton

History
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Democritus - First to use the term atom
Aristotle - Defined matter as composed of hot,
cold, wet and dry
John Dalton - Modern Atomic Theory and Law
of Multiple Proportions
Antoine Lavoisier - Law of conservation of
mass
Joseph Proust - Law of Definite Proportions
J.J. Thomson - Discovered the electron with
cathode ray experiment and proposed Plum
pudding model
Robert Millikan - Discovered the charge/mass
of the electron using Oil Drop Experiment
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Ernest Rutherford - Discovered the nucleus using
gold foil experiment
James Chadwick - Discovered the neutron
Henri Becquerel - discovered radiation emitted by
Uranium
Marie Curie - discovered two other elements that
emitted radiation (Polonium and Radium)
Niels Bohr - Proposed energy levels and the
Planetary model of the Atom
Louis de Broglie - Proposed the wave particle
duality of nature
Werner Heisenberg - Proposed the Uncertainty
Principle
Erwin Schrodinger – Proposed electron cloud
model (quantum mechanical model) of an atom
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John Newlands – noticed pattern when elements
were arranged by atomic mass (repeated every 8th
element). He used the word periodic to describe
this pattern and named it the Law of Octaves
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Lothar Meyer – made a connection between
atomic mass and properties of elements and made
periodic table
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Dmitri Mendeleev– made a connection between
atomic mass and properties of elements and made
periodic table. Also predicted unknown elements.
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Henry Mosely – arranged periodic table by atomic
number and gave us Periodic Law
Four parts of an experiment
Independent variable – what the scientist
changes, what is being tested.
 Dependent variable – what changes
because of the independent variable.
 Control – the comparison item, it is used to
see if the independent has an effect
(usually a sample with no independent
used)
 Constants – everything else that is in the
experiment that we keep constant
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