The History of the Atom 2: Dalton

What You Need

The History of the Atom 2: Dalton By Henry Roscoe (author), William Henry Worthington (engraver), and Joseph Allen (painter) [Public domain], via Wikimedia Commons


To explore early milestones in the development of modern atomic theory and the role of John Dalton.


This lesson is the second of a five-part series that will broaden and enhance students’ understanding of the atom and the history of its discovery and development from ancient to modern times.

The History of the Atom 1: The Ancient Greeks examines the ancient Greeks’ theories about the atom. This lesson explores early milestones in atomic theory and the role of John Dalton. The History of the Atom 3: The Periodic Table reviews the early development of the periodic table and its impact on atomic thought. The History of the Atom 4: J.J. Thomson analyzes the evolution of modern ideas on the inner workings of atoms and J.J. Thomson’s contributions. The History of the Atom 5: The Modern Theory investigates the development of modern atomic theory.

Greek philosophers Leucippus and Democritus first developed the concept of the atom in the 5th century B.C.E. However, since Aristotle and other prominent thinkers of the time strongly opposed their idea of the atom, their theory was overlooked and essentially buried until the 16th and 17th centuries. In time, Lavoisier’s groundbreaking 18th-century experiments accurately measured all substances involved in the burning process, proving that “when substances burn, there is no net gain or loss of weight.” Lavoisier established the science of modern chemistry, which gained greater acceptance because of the efforts of John Dalton, who modernized the ancient Greek ideas of element, atom, compound, and molecule; and provided a means of explaining chemical reactions in quantitative terms. (Science for All Americans, pp. 153–155.)

As this series of lessons explores further discoveries in the configuration, bonding, and inner structures of atoms, students will come to realize how much more refined, modernized, and scientific atomic theory has become since the critical breakthroughs of Lavoisier and Dalton three centuries ago.

It is important for students to understand that the study of matter continues to this day, and that humankind’s millenniums-old effort to identify, understand, and document the nature of matter eventually created modern sciences like chemistry and continues to lead to countless, purposeful technological advancements and inventions—like the TVs and computers that make the quality of life for humankind more and more fulfilling, convenient, and sometimes troubling. Students also should come to realize that, over time, the ancients’ ideas of matter were often proven inaccurate through modern science.

In middle school, students should have become familiar with the early theories of matter and how they led to the work of Lavoisier and the birth of modern chemistry. This awareness will help students better understand the importance of John Dalton, and how he ultimately strengthened Lavoisier’s findings by ushering in “the consistent use of language, scientific classification, and symbols in establishing the modern science of chemistry.” (Benchmarks for Science Literacy, pp. 250–251.)

Ideas in this lesson are also related to concepts found in these Common Core State Standards:

  • CCSS.ELA-Literacy.RST.9-10.1 Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions.
  • CCSS.ELA-Literacy.RST.9-10.2 Determine the central ideas or conclusions of a text; trace the text’s explanation or depiction of a complex process, phenomenon, or concept; provide an accurate summary of the text.
  • CCSS.ELA-Literacy.RST.9-10.4 Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant togrades 9–10 texts and topics.
  • CCSS.ELA-Literacy.RST.9-10.5 Analyze the structure of the relationships among concepts in a text, including relationships among key terms (e.g., force, friction, reaction force, energy).
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Planning Ahead

For background information and perhaps for your more advanced students, you can consult Atomism.


Briefly review what students learned in The History of the Atom 1. Students should pull out their charts summarizing the atomic theories of the ancients. Use this as a basis for review, which is a prerequisite for this lesson.

Students should now be able understand the differences between the atomic ideas of Leucippus and Democritus—and those who opposed them, Eleatics and Aristotle. Briefly, they should be able to convey that the atomists believed that all matter was composed of atoms, which were infinitely small and indivisible, completely solid, homogeneous with no internal structure, and varied in their size, shape, and weight. Atoms also came with a void, which is an empty space between atoms that allows them to change and move. Of course, modern science has come to prove some of these theories to be wrong—for instance, that atoms were not completely solid but made up of mostly empty space (Rutherford) and were shown to have an internal structure (Thomson).

Remind students that Leucippus’ theories were first formed in response to the Eleatics, who believed that the “formative substance of the universe was the One, all encompassing, motionless mass that contained no empty space, void.” Students also learned that Aristotle (and the Catholic Church) opposed the atomists because they suggested “Godlessness” by asserting that “there is no end to the universe, since it was not created by any outside power.” As a result, the ideas of Leucippus and Democritus were written off for roughly 2,000 years.

Explain to students that having a strong, basic understanding of the ideas and differences of early atomic theorists will help them as they now move on to learn about the more modern views of scientists like Galileo Galilei, Francis Bacon, Robert Boyle, and Isaac Newton leading up to and including John Dalton, who is the focus of this lesson.

Remind students that taking a moment to bridge the 2,000-year gap between the ancients and these early modern scientists is important. By the 17th century, for example, alchemy and chemical experimentation in general was gaining ground and legitimacy as possessing insights about the universal laws of nature. Breaking down chemical reactions in terms of atoms was also (undeniably) taking place during this critical era in modern science.


Part One

Students should begin by using their Dalton student esheet to go to and read, Evolution of the Atomic Concept and the Beginnings of Modern Chemistry. Encourage students to learn about the 17th- and 18th-century scientists highlighted here—Galileo Galilei, Francis Bacon, Robert Boyle, and Isaac Newton. Since the readings may be lengthy in some places, tell students to scan, read through, and take notes on only those sections that relate to the scientists mentioned above. Students can use the Pre-Dalton Scientists student sheet to help guide them in their reading.

A Meeting of the Minds
Once students have enough information on each of these pre-Dalton figures, divide the class into small groups. Each group should take turns discussing the ideas, flaws, merits, purpose, and final contributions each of the four scientists made to the development of the modern atomic theory before Dalton. Encourage participants to point out how their ideas may have related to or been extensions of the theories of the ancient philosophers who may have first developed them. Students need to come away from the reading and discussion with an understanding about each figure and his contributions to the study and development of matter. You can find information about each of these scientists on the Pre-Dalton Scientists teacher sheet.

Part Two

Combined Readings on John Dalton
Now students should use their esheet to go to and read:

These resources will enable them to explore key links, glossaries, and other broader resources on Dalton. If possible, tell students to take the online quiz on Dalton’s atomic theory, since they can submit their answers electronically and receive immediate results and explanations.

The information covered on these sites is very similar, particularly in their assessments of how Dalton developed his chemical atomic theory and the four basic ideas supporting it. Make sure that students understand these points. Based on these readings, students should address the questions on the Dalton student sheet either in small groups or as a class. You can find answers to the questions on the Dalton teacher sheet.

During this study and throughout this series of lessons, address common misconceptions such as: some middle- and high-school students “may think that substances can be divided up into small particles, [but] they do not recognize the particles as building blocks, but as formed of basically continuous substances under certain conditions” (Pfundt, 1981). In the area of chemical change, research shows that “many students do not view chemical changes as interactions. They do not understand that substances can be formed by the recombination of atoms in the original substances. Rather, they see chemical change as the result of a separate change in the original substance, or changes, each one separate, in several original substances…” (Anderson, 1990). (Benchmarks for Science Literacy, pp. 336–337.)

Emphasize the point that Dalton, “the Father of Chemical Atomic Theory,” had a lot of help developing his groundbreaking ideas. The ancient Greeks, Newton, Lavoisier, and countless other theorists and scientists over the centuries provided the exceptional Dalton with enough ideas and chemical data to scrutinize and formally develop, affirm, and systematize chemical atomism. 


Depending upon the time you have available, assign the following for class work or as homework.

To evaluate students’ comprehension of the readings and how they support the key benchmarks of the lesson, ask each student to list the four basic ideas behind Dalton’s chemical atomic theory and elaborate on each of them in his or her own words. Describe for students briefly what their answers should include. Overall, students should be able to express how Dalton’s findings helped to provide “a physical explanation for reactions that could be expressed in quantitative terms.”


Follow this lesson with the other lessons in the history of the atom series: The History of the Atom 3: The Periodic Table, The History of the Atom 4: J.J. Thomson, and The History of the Atom 5: The Modern Theory.

If not done previously, encourage students to test their knowledge on chemical atomism by taking the online Quiz: Dalton’s Atomic Theory. Final scores with answers and explanations are automatically displayed and students are given the option to further test themselves by taking other quizzes. 

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Lesson Details

Grades Themes Project 2061 Benchmarks National Science Standards