Focus On Physical Science: California Grade 8

Lesson 3: Elements, Isotopes, and Ions—How Atoms Differ

Standards Check

1.
A(n) __________ is a substance that cannot be broken down into simpler substances. 7.b
A)metal
B)element
C)mixture
D)compound
2.
The atomic number of calcium is 20. How many protons does a calcium atom contain? 7.b
A)40
B)0
C)20
D)10
3.
A chlorine atom has 17 protons and 18 neutrons. How many electrons does it have? 3.f
A)17
B)1
C)35
D)18
4.
What do lithium, sodium, and potassium have in common? 3.f
A)They are all metalloids.
B)They are all nonmetals.
C)They all have two electrons in their outer energy levels.
D)They are all Group I elements.
5.
What do atoms of boron and aluminum have in common? 3.f
A)They are metalloids.
B)They are metals.
C)They have the same number of neutrons in their nuclei.
D)They have three electrons in their outer energy levels.
6.
A(n) __________ is a pure substance that contains two or more elements. 3.f
A)molecule
B)ion
C)compound
D)solution
7.
Carbon-14 is useful in determining __________. 7.b
A)the age of dead plants and animals
B)the age of sedimentary rock layers
C)the best method for the disposal of a radioactive sample
D)how fast a radioactive sample will decay
Grade 8
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