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Jan 1, 1000
Democritus
Democritus
The Greek Era (1000 BC-31BC)
Abdera, Greece
Things are actually classified according to their type of atom and how much void they have.
We know that atoms contain solid parts and empty space.
http://old.perseus.tufts.edu/GreekScience/Students/Marc/short_paper.html -
Newton
Newtown
1704
England
Everything has small, moving parts.
Atoms are made of moving particles.
http://atomictimeline.net/index.php -
Dalton
Dalton
1803
England
Atoms are spheres with mass.
Atoms have an “atomic weight”.
http://atomictimeline.net/index.php -
G.J.Stoney
G.J. Stoney
1894
Ireland
There are particles with negative charge- electrons.
Atoms contain electrons.
http://atomictimeline.net/index.php -
J.J. Thomson
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Planck
Planck
1900
Germany Quanta – tiny particles of energy (hot and glowing)
When particles get warm up, they move more, creating more heat.
http://atomictimeline.net/index.php -
Nagaoka
Nagaoka
1903
Japan Electrons circle around a positive particle.
Electrons (negative) revolve around the nucleus (positive).
http://atomictimeline.net/index.php -
Milikan
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E. Rutherford
E. Rutherford
1911
New Zealand
Nucleus: very dense, tiny, positive charge. And electrons are outside it.
The nucleus is positive in charge and very small and dense.
http://atomictimeline.net/index.php -
H.G.J. Mosely
H.G.J. Mosely
1914
England
The number of protons in the nucleus is the atomic number of an element.
Elements are on the periodic table in order of atomic number (how many protons they have.)
http://atomictimeline.net/index.php -
Bohr
Bohr
1922
Denmark
Shells of electrons orbiting nucleus.
The electrons are sorted in shells around the nucleus.
http://atomictimeline.net/index.php -
James Chadwick
James Chadwick
1932
England
Neutral atomic particle.
Neutrons in the nucleus.
http://atomictimeline.net/index.php