Name
Date
Understanding the Atom
Lesson 1 Atoms—Basic Units of Matter
Grade 8 Science Content Standards—3.a: Students know the structure of the atom and know it is composed of protons,
neutrons, and electrons.
Accept all reasonable
responses.
Scan the What You’ll Learn statements for Lesson 1. List three
topics that will be discussed.
1. the structure of the atom
2. basic particles of an atom
3. Dalton’s atomic theory
Review
Vocabulary Define mass using your book or a dictionary.
mass
property of a body that causes it to have weight in
a gravitational field
New
Vocabulary Write a paragraph using all of the vocabulary terms to show
their meanings.
atom
nucleus
An atom is one of the particles that make up all matter. Each
atom contains a nucleus in its center that contains most of its
mass. The nucleus is made up of positively charged protons and
proton
neutron
electron
neutral neutrons. The atom also contains electrons, which are
negatively charged particles that move in the space around the
nucleus.
Academic
Vocabulary Use your book or a dictionary to define proportion. Then use the
term in a sentence.
proportion
relation of one to another in terms of number, amount, or size;
The proportion of dogs to cats is three to two.
38
Understanding the Atom
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
matter
Name
Date
Lesson 1 Atoms—Basic Units of Matter
What is the
current atomic
model?
I found this information
on page
.
(continued)
Conclude why the atomic-force microscope is important to
scientists.
The atomic-force microscope allows scientists to see the
surfaces of individual atoms.
CA SE, pp. 174–175
Compare protons, neutrons, and electrons.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Particle
Is there
historical
evidence of
atoms?
Where Found
Charge
Proton
nucleus
+1
Neutron
nucleus
0
1.008701
Electron
space around
the nucleus
–1
0.000549
1.007316
Organize information about Democritus’s theory of the atom
using the concept map.
small, solid spheres
with no holes
indivisible
I found this information
on page
.
Democritus’s Theory
of the Atom
CA SE, p. 176
Accept all reasonable
responses.
Mass (amu)
empty space
between atoms
can move
Complete the statement to summarize what an atom is.
An atom of aluminum is the smallest piece that is still aluminum .
S UMMARIZE I T
Summarize three main ideas from the above sections.
Accept all reasonable responses. Atoms are made up of protons, neutrons, and
electrons. Protons and neutrons have a much greater mass than electrons have.
Democritus proposed that atoms were indivisible pieces of matter.
Understanding the Atom
39
Name
Date
Lesson 1 Atoms—Basic Units of Matter
Is there
historical
evidence of
atoms?
(continued)
Sequence the steps of Antoine Lavoisier’s experiments on
mercury (II) oxide. Complete the flow chart.
mercury (II) oxide
placed in sealed
container
I found this information
on page
.
sealed container
heated
liquid mercury
and oxygen gas
produced
CA SE, p. 177
Remind students
that some reactions
produce gases that
cannot be seen, butstill have mass.
Summarize the law of conservation of mass and the law of
definite proportions.
Law of Conservation of Mass: The mass of the products of a
reaction is always the same as the mass of the starting materials.
Law of Definite Proportions: Compounds always contain the
same elements in the same proportion by mass.
I found this information
on page
.
Students should include these five principles:
All matter is made up of atoms. Atoms are neither created
nor destroyed in chemical reactions. Atoms of different
elements combine in whole-number ratios. Each element is
made of a different kind of atom. The atoms of different
elements have different masses and properties.
CA SE, p. 178
Accept all reasonable
responses.
S UMMARIZE I T
Summarize three main ideas of the above sections.
Accept all reasonable responses. The law of conservation of mass states that the mass of
the products is always the same as the mass of the starting materials. The law of definite
proportions states that compounds always have the same elements in the same
proportion by mass. Dalton proposed an atomic model based on five key principles.
40
Understanding the Atom
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Create a concept map for the 5 principles of Dalton’s atomic
model.