Write a note on ancient view on atomic structure.
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Answer:
This lesson is the first 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.
This lesson examines the ancient Greeks’ theories about the atom. The History of the Atom 2: Dalton 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.)
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PLANNING AHEAD
This lesson should take two 45-minute class periods.
You may want to print out and make copies of these resources that students will read in the lesson if your students don't have access to computers with Internet access:
The Greek Concept of Atomos: The Indivisible Atom
The Atomists: Leucippus of Miletus and Democritus of Abdera
Democritus of Abdera
MOTIVATION
Before students begin their Internet exploration into the history of the atom, review their present knowledge by asking questions like these:
What is matter?
(Matter is anything that has mass and occupies space.)
What is an atom?
(An atom is the smallest particle of an element.)
What is an element?
(An element is a substance that cannot be broken down into simpler substances under ordinary conditions.)
Why do you think it is important to study the history of the atom?
(Answers will vary. Accept any answers.)
In what ways do you think the study of matter has affected our lives?
(Answers will vary. Accept any answers.)
As you discuss these ideas, be aware of common misconceptions that students may have. For example, students might consider matter to include “everything that exists is matter, including heat, light, and electricity.” They also might think that “matter does not include liquids and gases or that they are weightless materials.” Finally, they may consider the weight of matter as a “’felt weight’—something whose weight they can’t feel is considered to have no weight at all.” (Benchmarks for Science Literacy, pp. 336–337.) High-school students should be able to recognize these earlier misconceptions.
Activity—Time Travel: Greece, 5th century B.C.E.
As a way to pique students’ interest and focus the discussion, prompt students with the scenario below. Displaying an old map of Greece might enhance this experience.
“Imagine now, if you will, that you are able to travel back in time to the 5th century B.C.E. You find yourselves in ancient Greece in the presence of Leucippus and Democritus, the two philosophers credited with originating the concept of the atom. You have the privilege to observe the two men as they work on and discuss their ideas about the atom.”
Next, ask the following questions. It is not so important for students to come up with accurate answers as to try to comprehend the era, circumstances, and particulars that might have occurred when the atomic concept was first formed. Putting students in the sandals of the ancient Greeks also will help them better understand the bare-bones human thought process that was involved in developing these truly profound and otherwise unimaginable concepts.
Ask students:
What do you see? What are these men like?
Why are they talking about concepts?
What do you think their specific ideas are about the atom?
How do you think they have come to these conclusions? What tools, if any, are they using?
What is remarkable about what they are doing?
(Accept all answers, but ask students to offer explanations to support their views.)
The purpose of these exercises is to set up the lesson and establish students' level of awareness regarding the basic concepts and the critical early figures that first developed them.