September 6, 1766 to July 27, 1844
Five Main Points of Dalton's Theory:
- 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.
John says that atoms were one single part. There is nothing to put in or take out of the substance.
When Dalton created his model; electrons, protons, and nuclei had not been discovered.
He thought an atom was one solid thing that could not be broken down into other parts. Thus, he imagined an atom to look similar to a sphere.
How Did Dalton Discover This?
Dalton discovered his theory while researching gases. He found that gases can only be combined in certain ways even if they shared a common or same group of elements. Through experiments, he discovered something interesting, atoms. His gas research led him to believe that all elements can combine in fixed ratios.