John Dalton (1768 - 1828)

Current Atomic Model

1. Combined the following ideas to form his atomic theory
   1. elements cannot be broken down into simpler substances
   2. conservation of mass
   3. law of constant composition or definite proportions
2. Dalton's Atomic Theory - 1808
   1. All elements are composed of atoms (indivisible particles)
   2. All atoms of the same element are identical - in particular they have the same mass.
   3. The atoms of one kind of element are different from the atoms of all other elements - in particular the atoms of one element have a different mass than those of other elements.
   4. Atoms are indestructible and retain their identity in chemical reactions.
      
   5. Compounds are formed by joining atoms in specific whole number ratios.
3. Black box model of the atom. Even after 2000 years of the atomic concept the structure of the atom was unknown. At this point in history it was still thought to be the smallest unit of matter.

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