It was the English chemist, John Dalton, who put the pieces of the puzzle together and developed an atomic theory in 1803. Dalton 's atomic theory contains five basic assumptions:
- All matter consists of tiny particles called atoms.
- Atoms are indestructible and unchangeable.- Elements are characterized by the weight of their atoms.
- In chemical reactions, atoms combine in small, whole-number ratios.
- When elements react, their atoms may combine in more than one whole-number ratio.
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