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Atomic Models
Democritus to Rutherford
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Democritus Atomic Theory
1) All matter is composed of atoms, which are bits of matter too small to be seenThese atoms CANNOT be further split into smaller portions
2) There is a void, which is empty space between atoms
3) Atoms are completely solid4) Atoms are homogeneous, with no internal
structure5) Atoms are different in their sizes, shapes, weight,
arrangement, position…
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John Dalton (1766~~1844)
A New System of Chemical PhilosophyDeveloped the first useful atomic theory of matterGifted in for recognizing and interpreting patterns in experimental dataFirst to associate the idea of atoms with stoichiometry
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Dalton’s Atomic Model
1. All matter consists of tiny particles2. Atoms are indestructible and
unchangeable3. Elements are characterized by the mass
of their atoms4. When elements react, their atoms
combine in simple, whole-numberratios
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J. J. Thomson ( 1856~~1940)
Discovered electrons in 1891.
Cathode ray tubes
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A Cathode Ray Tube
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Rutherford (1871~~1937)
Discovered the nucleus in 1911
The gold foil experiment
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Rutherford’s solution to the enigma of explaining both large- and small-angle scattering, was the
nucleus
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All Rutherford had to do was explain how it all fit together
Well established that atomic radius is 10-8 cm
Thomson model spread the entire mass of the atom throughout that space
Rutherford put most of the mass of the atom at the center of the atom, in a space much, much smaller that the atom itself
this is thenucleus
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Empty space!!
If an atom were thesize of a baseball
stadium, The nucleus would
be the size of a PEA
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Structure of the Nucleus
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A Model of Helium
2 protons
2 neutrons
2 electrons
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Elements Chart
6C-1450Sn15P9F6C7N8O
22244.0032He01111.0081H
# Neutrons
# Electrons
# Protons
Mass#
Atomic Mass
Atomic #
Element Symbol
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Isotopes
Same Atomic Number, Different Atomic MassSame # of Protons, Different # of Neutrons
Hydrogen: 1 proton, 0 neutronsHeavy Hydrogen
(Deuterium): 1 proton, 1 neutronHeavier Hydrogen
(Tritium): 1 proton, 2 neutrons
Carbon~12: 6 protons, 6 neutronsCarbon~14: 6 protons, 8 neutrons
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Alkali Metals
Alkaline Earth MetalsBoron Family
Carbon Family
Nitrogen Family
Oxygen Family
Halogens
Noble GasesTransition Metals
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gasliquid
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Source of Images and Text
http://antoine.frostburg.edu/chem/senese/101/atoms/dalton.shtml
http://dbhs.wvusd.k12.ca.us/Rutherford-Model.html
