2.39. Dalton’s Atomic Theory http://www.ck12.org
2.39 Dalton’s Atomic Theory
- Explain why Dalton reintroduced the idea of the atom.
- State Dalton’s atomic theory.
- Describe Dalton’s billiard ball model of the atom.
You probably know what this sketch represents. It’s a model of an atom, one of the miniscule particles that make
up all matter. The idea that matter consists of extremely tiny particles called atoms was first introduced about 2500
years ago by a Greek philosopher named Democritus. However, other philosophers considered Democritus’ idea
ridiculous, and it was more or less forgotten for more than 2000 years.
Reintroducing the Atom
Around 1800, the English chemist John Dalton brought back Democritus’ ancient idea of the atom. You can see a
picture of Dalton 2.71. Dalton grew up in a working-class family. As an adult, he made a living by teaching and just
did research in his spare time. Nonetheless, from his research he developed one of the most important theories in
all of science. Based on his research results, he was able to demonstrate that atoms actually do exist, something that
Democritus had only guessed.
Dalton’s Experiments
Dalton did many experiments that provided evidence for the existence of atoms. For example: