ffine$ftHet*FGef the Atsm
6. How many more neutronsdoesthorium-230
have than protons?How many electronsdoes
thorium-230 have?
1. Use the periodic table to completethe
following table.
Element
Atomic
J{umber
Protons
Electrons
a. Li
87
b.
C.
93
80
d. Hg
e.
81
f.
75
g.B
7 . Show that the massnumber and the number of
protons are conservedin the following nuclear
'\tv + 2l$rn +
equation:
$ne.
8 . Give the massnumberof eachisotope.
a. Be with 5 neutrons
b. Ga with 39 neutrons
c. Si with 16 neutrons
Give the number of protons, electrons,and
neutronsin each of the following atoms.
a. t?9au
d. Ti with 26 neutrons
e. Give the atomic number of eachisotope.
b. f$ca
a, magnesium-Zl
c. ??Nu
b. bromine-79
c. antimony-121
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3 . Name each isotope,and write it in symbolic
notation.
a. atomic number 26; massnumber56
b. atomic number 29; mass number 64
c. atomic number 17: massnumber 37
't
1 0 . Neon hastwo isotopes:neon-10and neon-12.
a. Which isotopehas,thegreatermass?
b. Which has more neutrons?
c. Which has more protons?
E
d. Which has more electrons?
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4. How many protons, electrons,and neutronsare
in eachof the following isotopes?
a. uranium-235
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b. hydrogen-3
c. silicon-29
5 . How many neutronsdoes europium-151have?
What is the isotope'smassnumber?
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1 1 . Use the table below to calculatethe atomic
mass of elementX. Then use the periodic table
to identify the element. Show all your work.
Mass (amu)
PercentAbundance
16x
15.995
99.762
17x
16.999
0. 038
18x
17.999
0. 20
lsotope
Chemistry:Matter and Changeo Chapter4
12. Magnesiumhas threeisotopes.Magnesium-}
has a percentabundanceof 78.99VoMagnesium-26has a percent abundanceof
11.01Vo.Whatis the percentabundanceof
magnesium-Zl?Assume that there are no other
magnesiumisotoPes.
13. Calculatethe atomic mass of iridium. Iridium
has two isotopes.Iridium-191 has a massof
191.0amu and a percentabundanceof 3l .58To'
Iridium-191has a massof 193.0amu and a
percentabundince of 62.42Vo.Show all your
work.
An elementhas three naturally occumng
isotopes.
Isotopet has a massof 19.992amu.
Isotope2 has a massof 20.994 amu.
Isotope3 has a massof 2L.991amu.
The pie graph showsthe relative abundanceof
eachisotope.
lsotope2
0.27o/o
lsotope3
lsotope 1
90.51o/o
15. An elementhas three naturally occurring isotopes.Information about each isotopeis summarized below.
Mass(amu)
PercentAbundance
lsotope 1
23.985
78.10
lsotope2
24.946
10.3
1
lsotope3
25.983
11.17
lsotope
a. Find the atomic mass of this element.Show
all your work.
b. Identify the element,using the periodic
table.
Write each isotope in symbolic notation.
16. The isotopecarbon-14can be usedto determine the agesof objects that were once living,
such as wood, bones,and fossils.While alive,
living things take in all the isotopesof carbon,
including carbon-14. Carbon-I4 undergoes
radioactivedecay continuously.After an organism dies, the carbon-14in its body continuesto
decay.However, its body no longer takesin
new carbon-l4. Thus, by measuringhow much
carbon-14a once-livingobject containsand
comparing it with the amount of carbon-14 rn a
currently living thing, you can determinethe
age of the object.
a. In terms of subatomic structure,how does
carbon-14differ from carbon-12 and
carbon-13?
b. How is carbon-14like carbon-12and
carbon-13 ?
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Carbon-14emits a beta particle as it decays.
What atom does carbon-14 decaYto?
Calculatethe atomic mass of the element.
Write an equation to representthe decay of
carbon-14.
Identify the element,using the periodic
table.
Chemi s tryM
: a tte r a n d C h a n g e' C h apter4
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