Download Rutherford Scattering

Development of Atomic
Structure
How long have people been interested in
understanding matter and its structure?
A. Thousands of years
B. Hundreds of years
C. A few years
D. Never
Democritus (ca. 450 BC)
Ancient Philosophy
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Who: Aristotle, Democritus
When: More than 2000 years ago
Where: Greece
What: Aristotle believed in 4 elements: Earth, Air,
Fire, and Water. Democritus believed that
matter was made of small particles he named
“atoms”.
• Why: Aristotle and Democritus used observation
and inference to explain the existence of
everything.
Alchemists
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Who: European Scientists
When: 800 – 900 years ago
Where: Europe
What: Their work developed into what is
now modern chemistry.
• Why: Trying to change ordinary materials
into gold.
Alchemic Symbols
John Dalton (1766-1844)
Dalton’s Atomic Theory (18030
1) All matter is made of atoms. Atoms are
indivisible and indestructible.
2) All atoms of a given element are identical
in mass and properties
3) Compounds are formed by a combination
of two or more different kinds of atoms.
4) A chemical reaction is a rearrangement
of atoms.
Wilhelm Roentgen (ca. 1895)
Henri Becquerel
Marie Curie ca. 1920. Inset: Pierre Curie (Marie's
favorite picture of her husband).
Ernest Rutherford
Rutherford Scattering: Nuclear Model
• Rutherford scattering probes the atom. (Hit it with something!)
– Beam of a particles (He2+) strikes a thin gold metal foil.
– Atoms in the foil scatter the alpha particles through various
scattering angles q that are detected with a scintillation
screen.
– 180º scattering can occur (“back bounce”), indicating a
“hard core” interaction between the a particles and atoms
in the foil.
• “Nuclear” model by Rutherford explains large scattering angles.