/•»AVERAGE AlOMIC MASS
/•**^en the following data:
atomic mass 37CI: 36.97
(24.2%
in nature)
atomic mass ^^ci: 34.97
(75.8%
in nature)
Average
Find average atomic mass of chlorine.
atomic mass of first isotope
atomic mass of next isotope
^^omic =
times
+
times
+.
''^lass
percent of isotope in nature • percent of isotope in nature
Average
atomic
=
34.97 x 75.8% +
36.97 x 24.2%
mass
Average
atomic
=
26.51 + 8.95
mass
Average
atomic
= 35.46 = 35.5, rounded off to one decimal place.
mass
8-2
Teaching Master 6
Macmillan Publishing Company
Name
Date
Period
ISOTOPES
1. Magnesium has 3 isotopes which occur in nature as follows:
Mg-24
Mg-25
Mg-26
79%
10%
11%
Use this information to calculate the average atomic mass for magnesium.
(jl ) '
2. Copper consists of two isotopes as follows:
Cu - 63
69.2%
Cu - 65
30.8%
Calculate the average atomic mass of copper.
it ^ C'
^ ~ •D
3. Silver has two naturally occurring isotopes.
Ag - 107 has an abundance of 51.8%. The other isotope is Ag - 109.
Calculate the average atomic mass of silver.
/^
r// ) =yr,
/
.
Average Atomic Mass Worksheet
1)
Rubidium hastwo common isotopes,
and ®^Rb. If the abundance of
Rb is 72.2% and the abundance of ®^Rb Is 27.8%, what fs the average
atomic mass of rubidium?
^
\
(-1^)
2)
Uranium hasthree common isotopes. If the abundance of
the abundance of
is 0.71 %. and the abundance of
is 0 01%
is 99.28%, '
what is the average atomic mass of uranium?
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. ^
• LSrCc!
common isotopes: "*^71 (8.0%), "^^Ti (7.8%),
(73.4%),
^i(5.5%), °Ti(5.3%). What is the average atomic mass of titanium?
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<3' ^ 7
(<0'^-^ —<x>
fZ
4)
Explain why atoms have different isotopes. In other words, how isit that
helium can exist in three different forms?
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4. An imaginary element Q consists of 2 isotopes, The abundance of
Q - 212- is 48%. Ifthe average atomic mass for Q is 207.92 amu,
what is the other isotope of Q?