The Historical View of
Atomic Structure Continued
What is an Atom?
The smallest particle of an element
that retains the properties of the
element.
Dalton’s Billiard Ball Model
Dalton’s Five Part Model
 Elements are made of extremely small particles
called atoms.
 Atoms of a given element are identical in size,
mass, and other properties; atoms of different
elements differ in size, mass, and other properties.
 Atoms cannot be subdivided, created, or destroyed.
 Atoms of different elements combine in simple
whole-number ratios to form chemical compounds.
 In chemical reactions, atoms are combined,
separated, or rearranged.
J.J. Thompson
Late 1890’s Plum Pudding Model
 Contribution: Atoms are divisible (a
negative charge exists)
 Evidence/Method: Cathode ray tube
experiments
http://www.youtube.com/watch?feature=playe
r_embedded&v=XU8nMKkzbT8
J. J. Thompson's Atomic Model
Robert Millikan
1909
Contribution: Accurate charge of an
electron
Evidence/Method: Oil drop
experiment
http://www.kentchemistry.com/links/Ato
micStructure/Millikan.htm
Ernest Rutherford

1911
Contribution: Atoms are mostly empty
space with a central positive mass he
called the nucleus
Evidence/Method: Gold foil experiment
http://www.kentchemistry.com/links/At
omicStructure/RutherfordTutorial.htm
Rutherford’s Atomic Model
James Chadwick
 1932
 Contribution: Discovered the neutron, the
neutral particle in the nucleus of the atom,
 Evidence/Method: He did this by bombarding
atom’s nuclei with alpha particles. In doing this
he could study the structure of the atoms
nucleus.
 http://www.kentchemistry.com/links/Atomic
Structure/Chadwick.htm
Chadwick’s Atomic Model
Acknowledgements
o Image Source Page:
o http://www.squidoo.com/chemistry-lapbook
 John Dalton’s Atomic Model
 http://lindseylester.wordpress.com/science-courses/science10/unit-a/lesson-2-atomic-theory/
 J. J. Thompson’s Atomic Model
 http://reichchemistry.wikispaces.com/1875AD-1900AD
 Chadwick’s Atomic Model
 http://reich-chemistry.wikispaces.com/mcgilvray-munsey