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The Solid Sphere Model

By the early 1800’s, the Law of Definite Composition and the Law of Multiple Proportions were commonly accepted ideas concerning the behavior of matter.

  • Law of Definite Composition states that in any sample of a compound the masses of the elements are in the same ratio.
  • Law of Multiple Proportions states that when two elements combine to form more than one compound, the fixed amounts of one element will combine with the other in a ratio of small whole numbers

Influenced by these concepts, John Dalton, a Quaker tutor, took these ideas and the work of others and devised the first atomic model based on empirical evidence.

Dalton’s Postulates

  1. All matter consists of tiny, indivisible, indestructible particles called atoms.
  2. Atoms of the same element have the same size, mass and chemical properties.
  3. Differences in the properties of elements result from differences in the atoms of the elements.
  4. The atoms in a compound combine in a definite, simple, whole number ratio.
  5. A chemical reaction is the result of rearrangement, combination, or separation of atoms.


“We might as well attempt to introduce a new planet into the solar system,
or to annihilate one already in existence, as to create or
destroy a particle of hydrogen.” – John Dalton