Page 16 - Utah Science Textbook
P. 16
History of Atomic Theory
Democritus Introduces the Atom
The history of the atom begins around 450 B.C. with a Greek philosopher named
Democritus (see Figure 2). Democritus wondered what would happen if you cut a piece of
matter, such as an apple, into smaller and smaller pieces. He thought that a point would be
reached where matter could not be cut into still smaller pieces. He called these
"indivisible" pieces atomos. This is where the modern term atom comes from.
Democritus was an important philosopher.
However, he was less influential than the Greek
philosopher Aristotle, who lived about 100 years
after Democritus. Aristotle rejected Democritus’s
idea of atoms. In fact, Aristotle thought the idea of
atoms was ridiculous. Unfortunately, Aristotle’s
ideas were accepted for more than 2000 years.
During that time, Democritus’s ideas were more or
less forgotten.
Dalton Brings Back the Atom
Around 1800, a British chemist named John Dalton
revived Democritus’s early ideas about the atom.
Dalton is pictured in Figure 3. He made a living by
teaching and just did research in his spare time.
Figure 2 Nonetheless, from his research results, he developed
one of the most important theories in science.
Dalton's Research
Dalton did many experiments that provided
evidence for atoms. For example, he studied the
pressure of gases. He concluded that gases must
consist of tiny particles in constant motion. Dalton
also researched the properties of compounds. He
showed that a compound always consists of the same
elements in the same ratio. On the other hand,
different compounds always consist of different
elements or ratios. This can happen, Dalton
reasoned, only if elements are made of tiny particles
that can combine in an endless variety of ways. From
his research, Dalton developed a theory of the atom.
You can learn more about Dalton and his research
by watching the video at this URL:
Figure 3 http://www.youtube.com/watch?v=BhWgv0STLZs (9:03).
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Democritus Introduces the Atom
The history of the atom begins around 450 B.C. with a Greek philosopher named
Democritus (see Figure 2). Democritus wondered what would happen if you cut a piece of
matter, such as an apple, into smaller and smaller pieces. He thought that a point would be
reached where matter could not be cut into still smaller pieces. He called these
"indivisible" pieces atomos. This is where the modern term atom comes from.
Democritus was an important philosopher.
However, he was less influential than the Greek
philosopher Aristotle, who lived about 100 years
after Democritus. Aristotle rejected Democritus’s
idea of atoms. In fact, Aristotle thought the idea of
atoms was ridiculous. Unfortunately, Aristotle’s
ideas were accepted for more than 2000 years.
During that time, Democritus’s ideas were more or
less forgotten.
Dalton Brings Back the Atom
Around 1800, a British chemist named John Dalton
revived Democritus’s early ideas about the atom.
Dalton is pictured in Figure 3. He made a living by
teaching and just did research in his spare time.
Figure 2 Nonetheless, from his research results, he developed
one of the most important theories in science.
Dalton's Research
Dalton did many experiments that provided
evidence for atoms. For example, he studied the
pressure of gases. He concluded that gases must
consist of tiny particles in constant motion. Dalton
also researched the properties of compounds. He
showed that a compound always consists of the same
elements in the same ratio. On the other hand,
different compounds always consist of different
elements or ratios. This can happen, Dalton
reasoned, only if elements are made of tiny particles
that can combine in an endless variety of ways. From
his research, Dalton developed a theory of the atom.
You can learn more about Dalton and his research
by watching the video at this URL:
Figure 3 http://www.youtube.com/watch?v=BhWgv0STLZs (9:03).
17
