Download Properties of Atoms and the Periodic Table

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Properties of Atoms and the Periodic Table
Section 2 Masses of Atoms
Preview Section 2 of your book, using the checklist below.
• Read all section titles.
• Read all boldfaced words.
• Read all charts and graphs.
• Look at all the pictures and read their captions.
• Think about what you already know about masses of atoms.
Write three facts you learned.
1. Accept all reasonable answers. Protons identify an element.
2. Radioactive isotopes are used to measure the age of fossils.
3. An electron’s mass is negligible.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Review
Vocabulary Define mass to show its scientific meaning.
mass
amount of matter in an object
New
Vocabulary Use your book or dictionary to define the following key terms.
atomic number
mass number
isotope
average atomic mass
a number equal to the number of protons in an atom’s nucleus
sum of the number of protons and neutrons in an atom
atoms of the same element with different numbers of neutrons
the average mass of the mixture of isotopes of an element
Academic
Vocabulary Use a dictionary to find the scientific meaning of define.
define
to determine or identify the essential qualities or meaning of
something
Properties of Atoms and the Periodic Table
195
Name
Date
Section 2 Masses of Atoms
Atomic Mass
I found this information
on page
.
SE, pp. 494–495
RE, p. 284
(continued)
Organize the information on atomic mass to complete the outline.
Atomic Mass
A. Nucleus of atom
1. contains most of the mass of an atom
2. masses of protons and neutrons in a nucleus are
nearly identical
3. electron’s mass is so small it is not included in atomic
mass
B. Atomic mass unit
1. amu appropriate unit for measuring the size of a particle
2. equals one-twelfth the mass of a carbon atom
C. Protons
1. number of protons is used to identify elements
2. each element has different number of protons
3. number of electrons equals the number of protons
in an element
4. number of protons equals the atomic number of the
element
D. Mass number
1. equals the sum of the number of protons plus neutrons
of an atom
2. atoms of the same element can have different number
of neutrons and a different mass number
196
Properties of Atoms and the Periodic Table
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3. each proton and each neutron has a mass of about 1 amu
Name
Date
Section 2 Masses of Atoms
Isotopes
I found this information
on page
.
SE, pp. 496–497
RE, p. 286
(continued)
Model carbon-12 and carbon-14 by sketching each atom.
• Remember that carbon’s atomic number is 6.
• Label each atom’s protons, neutrons, and electrons.
• Show the charges of the particles.
Student drawings should
resemble figure on
SE p. 515 or RE p. 291,
but with 6 protons, and
6 neutrons.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Carbon-12
Student drawings should
resemble figure on
SE p. 515 or RE p. 291,
but with 6 protons, and
8 neutrons.
Carbon-14
Analyze how you would determine which isotope of an element is
the most abundant if you know the element’s average atomic mass.
Accept all reasonable answers. Round the average atomic mass
to the nearest whole number to find the most abundant isotope.
CONNECT IT
While exploring on your grandfather’s farm, you come across
what appears to be ancient Native American artifacts, arrowheads, and tools. Explain
how you could find out the age of these pieces and if they are, in fact, an archeological
find.
Accept all reasonable answers. Student answers should describe the use of carbon-14,
explanation of half-life, and radioactivity to identify organic parts of the artifacts.
Properties of Atoms and the Periodic Table
197