Topics: Atom, Electric charge, Neutron Pages: 5 (647 words) Published: December 4, 2012
Name ___________________________
Chapter 4

Class ___________________

Date _____________

Atomic Structure

Section 4.1 Studying Atoms
(pages 100-105)
This section discusses the development of atomic models.

Reading Strategy (page 100)
Summarizing As you read, complete the table about atomic models. For more information on this Reading Strategy, see the Reading and Study Skills in the Skills and Reference Handbook at the end of your textbook.

Atomic Models




Ratio of masses
in compounds

Indivisible, solid spheres


Deflected beam

Negative charges evenly scattered through
positively charged mass of matter
(plum pudding model)


Deflection of alpha particles
passing through gold foil

Positive, dense nucleus

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Ancient Greek Models of Atoms (page 100)
1. Democritus named the smallest particles of matter
because they could not be divided.
2. List the four elements that Aristotle included in his model of matter. Earth

Dalton’s Atomic Theory

(page 101)

3. Is the following sentence true or false? John Dalton gathered evidence for the existence of atoms by measuring the masses of true
elements that reacted to form compounds.
4. What theory did Dalton propose to explain why the elements in a compound always join in the same way? He proposed that all matter is made up of individual particles called atoms, which cannot be divided.

5. Circle the letters of the sentences that represent the main points of Dalton’s theory of atoms.
a. All elements are composed of atoms.
b. In a particular compound, atoms of different elements always combine the same way.
c. All atoms have the same mass.
d. Compounds contain atoms of more than one element.
Physical Science Reading and Study Workbook


Chapter 4


Name ___________________________
Chapter 4

Class ___________________

Date _____________

Atomic Structure

Thomson’s Model of the Atom

(pages 102–103)

6. Objects with like electric charges
, and objects with
opposite electric charges
7. What happened to the beam when Thomson placed a pair of charged metal plates on either side of the glass tube? The beam was attracted by the positively charged plate and repelled by the negatively charged plate.

8. Thomson concluded that the particles in the glowing beam had a(n) negative
charge because they were attracted to a positive plate.
9. Is the following sentence true or false? Thomson’s experiments provided the first evidence for the existence of subatomic particles. true

10. Describe Thomson’s model.

Negative charges are evenly scattered throughout an atom filled

with positively charged mass of matter.

Rutherford’s Atomic Theory
11. What is an alpha particle?

(pages 104–105)

An alpha particle is a fast-moving particle that carries

a positive charge.

12. Fill in the table to show what Rutherford hypothesized would happen to the paths of alpha particles as they passed through a thin sheet of gold.
Rutherford’s Hypothesis
Particles that did not pass straight

from their source to a screen that lit up

through would be deflected only slightly.

when struck.

13. Circle the letters of the sentences that describe what happened when Marsden directed a beam of particles at a piece of gold foil. a. Fewer alpha particles were deflected than expected.
b. More alpha particles were deflected than expected.
c. None of the alpha particles were deflected.
d. Some alpha particles bounced back toward the source.
14. Circle the letter of the sentence that states what Rutherford concluded from the gold foil experiment.
a. An atom’s negative charge is concentrated in its nucleus. b. Thomson’s model of the atom was correct.
c. An atom’s positive charge is concentrated in its...
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