Learning Target: Use isotope notation to determine: element name/symbol, atomic number, number of
electrons, number of neutrons, number of protons, mass number, atomic number, atomic mass.
Isotope Notation: Fill in the chart below. You will need to use your periodic table.
Element
Symbol
Atomic
number
helium
Ti
Number of
electrons
2
Number of
neutrons
2
22
73
gallium
Mass
number
Isotope
notation
50
68
108
28
39
13
6
83
83
Atomic
mass
C "4
127
!
226
88
Ra
Learning target: Given the isotopes of an element and the percent of each isotope, determine the average
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atomic mass of the element.
Learning target: Explain how atomic masses in the periodic table are derived.
Answer the questions below in the space provided. Show work, use sig figs, use units. Circle your answers.
1. Boron has two naturally occurring isotopes: boron-10 (abundance = 19.8 %, mass = 10.013 amu) and
boron-11 (abundance = 80.2%, mass = 11.009 amu). Calculate the (average) atomic mass of boron.
2. Copper has two isotopes: Cu-63 (abundance = 69.2%, mass = 62.930 amu) and Cu-65 (abundance =
30.8%, mass = 64.928 amu). Calculate the (average) atomic mass of copper.
3. Three magnesium isotopes have atomic masses and relative abundances of 23.985 amu (78.99%),
24.986 amu (10.00%), and 25.982 (11.01%). Calculate the (average) atomic mass of magnesium.
There are more questions on the other side of this page.
4. Using to following data, calculate the (average) atomic mass of unknown Element X. Then, identify
the unknown element, which is used medically to treat some mental disorders.
Isotopic Abundance for Element X
Isotope
Mass (amu)
6
X
6.015
7
X
7.016
Percent Abundance
7.59
92.41
5. Nitrogen has two naturally occurring isotopes, N-14 and N-15. Its atomic mass is 14.007. Which
isotope is more abundant? Explain your answer.
6. Data for chromium’s four naturally occurring isotopes are provided in the table below. Calculate
chromium’s (average) atomic mass.
Chromium isotope data
Isotope
Cr-50
Cr-52
Cr-53
Cr-54
Mass (amu)
49.946
51.941
52.941
53.939
Percent Abundance
4.35
83.79
9.50
2.36
7. Silver has two isotopes: 107
47 Ag , which has a mass of 106.905 amu and a percent abundance of
109
52.00%, and 47 Ag , which has a mass of 108.905 amu and a percent abundance of 48.00%. What is
the (average) atomic mass of silver?
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