Mass Reactants = Mass products
Proust expanded on LaVoisier’s
experiments. (1797)
•He decomposed CuCO3 into
Cu + C + O and measured the masses
of each separately.
• The ratio of the masses were always
1:1:3 regardless of the sample source
or size.
John Dalton 1808
Dalton's Atomic Theory
1) All matter is made of atoms.
2.) Atoms are indivisible and
indestructible.
Dalton's Atomic Theory
3) All atoms of a given element
are identical in size, mass and
properties.
Dalton's Atomic Theory
4) Compounds are formed by
atoms that combine in whole
numbers.
Dalton's Atomic Theory
5) A chemical reaction is a
rearrangement of atoms.
+
+
1890
Cathode Ray Experiments
JJ Thomson (1897)
• Plum pudding model
• Cathode ray tube—electrons can be attracted and
repelled by a magnet
• Tiny negative particles stuck inside a sphere of
positively charged stuff.
Robert Millikan
The Oil Drop Experiment (1909)
It allowed the mass & charge
of an electron to be determined.
http://www.youtube.com/watch?v=XMfYHag7Liw
Ernest Rutherford (1911)
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf
Rutherford
Model of the Atom
+
Niels Bohr (1913)
• Electrons have specific levels that they orbit
around the nucleus.
• Can see this in the colors that different elements
emit
deBroglie or Quantum
Model of the Atom
Electrons move as waves in orbitals.
James Chadwick (1932)
• While measuring the mass of atoms,
discovered the neutron in the nucleus