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Name ____________________________________________________________ Date ___________________
The Structure of the Atom
Before You Read
Define the following terms.
scientific law
describes a relationship in nature that is supported by many
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experiments
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theory
an explanation supported by many experiments; is still subject
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to new experimental data, can be modified, and is considered
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successful if it can be used to make predictions that are true
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element
a pure substance that cannot be separated into simpler
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substances by physical or chemical means
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law of definite
proportions
states that regardless of the amount, a compound is always
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composed of the same elements in the same proportion by mass
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law of multiple
proportions
states that when different compounds are formed by a combination
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of the same elements, different masses of one element combine with
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the same mass of the other element in a ratio of small whole numbers
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Describe three things that you already know about the atom.
Accept all reasonable responses.
1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________
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Name ____________________________________________________________ Date ___________________
The Structure of the Atom
Section 1 Early Ideas About Matter
Scan Section 1 of your text. Use the checklist below as a guide.
 Read all section titles.
 Read all boldfaced words.
 Read all tables and graphs.
 Look at all pictures and read the captions.
 Think about what you already know about this subject.
List three things you expect to learn about while reading the section.
Accept all reasonable responses.
1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________
Use your text to define each term.
Dalton’s atomic theory
a theory proposed by John Dalton in 1808, based on numerous
________________________________________________________
scientific experiments, which marked the beginning of the
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development of modern atomic theory
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Name ____________________________________________________________ Date ___________________
Section 1 Early Ideas About Matter (continued)
Greek
Philosophers
Use with pages 102–103.
Summarize the effect that Aristotle had on the atomic theory proposed
by Democritus.
Aristotle rejected Democritus’s ideas because they did not agree with his ideas
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on nature. He did not believe that the “nothingness” of empty space could
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exist. He denied the existence of atoms. People accepted Aristotle’s
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conclusions for 2,000 years, and the ideas of Democritus were not developed.
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John Dalton
Use with pages 104.
List the main points of Dalton’s atomic theory.
All matter is composed of extremely small particles called
1. ______________________________________________________
atoms.
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All atoms of a given element are identical in size, mass, and
2. ______________________________________________________
chemical properties. Atoms of one element are different from
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those atoms of any other element.
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Atoms cannot be created, divided into smaller particles, or
3. ______________________________________________________
destroyed.
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Different atoms combine in simple whole-number ratios to
4. ______________________________________________________
form compounds.
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In a chemical reaction, atoms are separated, combined, or
5. ______________________________________________________
rearranged.
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Discuss Dalton’s ideas by completing the following paragraph.
chemical reactions
After years of studying ______________________,
Dalton was able to
mass ratios of the elements involved in the
accurately determine the ______________
atomic theory which helped to
reactions. His conclusions resulted in the _______________,
atoms in chemical reactions separate, _____________,
combine or
explain that _________
rearrange
destroyed
divided
________________,
but are not created, ______________,
or____________.
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Science Notebook
Name ____________________________________________________________ Date ___________________
Section 1 Early Ideas About Matter (continued)
Compare and contrast the atomic theories of Democritus and Dalton.
Mark an X under each name if a statement in the table applies to that
person’s theory.
Statement
Democritus
Dalton
All matter is made of tiny pieces.
x
x
Matter is made of empty space
through which atoms move.
x
Atoms cannot be divided.
x
x
Atoms cannot be created.
x
x
Atoms cannot be destroyed.
x
x
x
Different atoms combine in
whole-number ratios to form
compounds.
The properties of atoms vary
based on shape, size, and
movement.
x
Different kinds of atoms come in
different sizes and shapes.
x
REAL-WORLD CONNECTION
The experiments of the alchemists revealed the properties of some metals and provided the foundation for the
science of chemistry. Although not successful, alchemy proved beneficial to science. Explain how this example
can be applied to modern research.
Accept all reasonable responses. Possible answer: Even research and experiments that do
________________________________________________________________________________
not succeed add to our body of knowledge and provide useful information to later
________________________________________________________________________________
researchers.
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