History of Modern Atomic Theory
by Dominic L.
Timeline of the Evolution of the Atomic Model:
Greeks Dalton Thomson Rutherford Bohr Wave
Created in 400 B.C.
Democritus concluded that matter could be divided and divided until it cannot be divided any more
He called the particle that could not be divided an atom
created in 1803 by John Dalton
All elements are composed of indivisible particles
Atoms of the same element are exactly alike
Atoms of different elements are not alike
Compunds are formed by joining atoms of two or more elements
Created 1897 by J.J. Thomson
Said that the atom consists of positively charged protons and negatively charged electrons
proved that an atom could be divided
said the atom is neutral
Created in 1809
showed that the Atom has a nucleus
inside the nucleus are protons and neutrons
the nucleus's size can be compared to a bee in a stadium
outside the nucleus are the electrons in the electric cloud
discovered this by shooting charged particles through a gold sheet and counting the number of particles that went through
said the electrons orbit around the nucleus like the planets orbit around the sun
created in 1913 by Niels Bohr
Electrons orbit around the nucleus in a definite orbit
proposed that electrons move in specific energy levels
Based on wave mechanics
proposed that electrons do not move in a definite orbit and that the location of the electrons is based on how much energy each electron contains
References
The Atomic Model. March 11, 2002. <http://pc65.frontier.osrhe.edu/hs/science/pmodel.htm>
PICTURES
http://search.yahoo.com/search?p=Rutherford+Model
http://www.aip.org/history/electron/
http://pc65.frontier.osrhe.edu/hs/science/pmodel.htm
