Dalton By Henry Roscoe (author), William Henry Worthington (engraver), and Joseph Allen (painter) [Public domain], via Wikimedia Commons


In this lesson, you will explore early milestones in the development of modern atomic theory and the role of John Dalton in the modernization of the ancient Greek ideas of element, atom, compound, and molecule. To do so, you will study several online resources to gain more information about the history of the atom.


To begin, you should read about some 17th- and 18th-century scientists, including Galileo Galilei, Francis Bacon, Robert Boyle, and Isaac Newton by reading Evolution of the Atomic Concept and the Beginnings of Modern Chemistry. As you read this resource, you should take notes on each of the scientists on your Pre-Dalton Scientists student sheet. Pay careful attention to their ideas, flaws, merits, purpose, and final contributions.

Now you should explore the key links, glossaries, and other broader resources on John Dalton by reading these resources:

As you look at these resources, you should answer these questions on your Dalton student sheet:

  • What is the difference between physical and chemical atomism?
  • How did Dalton come to develop his chemical atomic theory?
  • What did Dalton ultimately wish to determine or prove?
  • What are the four basic ideas of Dalton’s chemical atomic theory?
  • Where, if any, was the work of Dalton proven to be incorrect?
  • What is seen as the “original contribution” of Dalton?
  • What is the Law of Conservation of Mass?
  • What is the significance of Dalton’s work?

If you have time, you can do the Quiz: Dalton's Atomic Theory to review what you have learned. 

This esheet is a part of the The History of the Atom 2: Dalton lesson.

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