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KS3 Science - Atomic History Timeline: Dalton

How ideas about the atom developed - evolution of the atomic model

John Dalton

John Dalton (1766–1844) was born into a modest Quaker family in Cumberland, England, and earned his living for most of his life as a teacher and public lecturer, beginning in his village school at the age of 12. After teaching 10 years at a Quaker boarding school in Kendal. 

source: Grolier.com

Short Quiz on Dalton's atomic theory

(Click on picture to access quiz)

Watch a video - Dalton Atomic Theory

Drawbacks of Dalton's model

  • No mention  of  nucleus
  • Does not explain ions or isotopes
  • Does not talk about subatomic particles

Dalton's Atomic Theory

Main points

** Atoms seens as solid indestructible spheres

** Explains many chemical properties


(These wooden balls, were the first models made to represent atoms and were used by John Dalton (1766-1844) to demonstrate atomic theory)

The atomic theory was first explicitly stated by Dalton at a Royal Institution lecture in December 1803. The basic postulates of the theory are that matter consists of atoms; that atoms can neither be created nor destroyed; that all atoms of the same element are identical, and different elements have different types of atoms; that chemical reactions take place by a rearrangement of atoms; and that compounds consist of compound atoms" formed from atoms of the constituent elements.

source: Grolier.com

Quote from Dalton

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, A New System of Chemical Philosophy, (1808) 

Foundation of Atomic Theory

(Dalton's handwritten notes)

  1. All matter consists of tiny particles.
  2. Atoms are indestructible and unchangeable.   
  3. Elements are characterized by the mass of their atoms.
  4. When elements react, their atoms combine in simple, whole-number ratios.
  5. When elements react, their atoms sometimes combine in more than one simple, whole-number ratio.
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