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Elements: Calculating Isotopic Abundances
Related Topics
Wize University Chemistry Textbook > Atoms, Ions, & Isotopes
Isotopes and Atomic Weight
4 Activities
There are two naturally occurring and stable isotopes of lithium,
6
Li (6.0151 amu) and
7
Li (7.0160 amu). What is the abundance of
7
Li in naturally occurring Lithium?
50%
84.4%
15.6%
92.5%
7.5%
I don't know
Check Submission
More Isotopes and Atomic Weight Questions:
Practice: Isotopes
An atom with 6 neutrons and a mass number of 13 is an isotope of which element?
Elements: Isotopes
Bromine is a noxious fuming red liquid in its elemental form. Naturally occurring bromine has two stable isotopes
79
Br (78.918
u
) and
81
Br (80.916
u
). What are the relative abundances of these two isotopes?
Enter your answer as a percentage (ex. If the answer is 16.26%, enter 16.26 as the answer)
The natural abundance of Bromine is 79.904 g/mol
Elements: Isotopes
Bromine is a noxious fuming red liquid in its elemental form. Naturally occurring bromine has two stable isotopes
79
Br (78.918
u
) and
81
Br (80.916
u
). What are the relative abundances of these two isotopes?
Enter your answer as a percentage (ex. If the answer is 16.26%, enter 16.26 as the answer)
Elements: Isotopes
Bromine is a noxious fuming red liquid in its elemental form. Naturally occurring bromine has two stable isotopes
79
Br (78.918
u
) and
81
Br (80.916
u
). What are the relative abundances of these two isotopes?
Enter your answer as a percentage (ex. If the answer is 16.26%, enter 16.26 as the answer)
Elements: Isotopic Mass
Fe has three isotopes in relatively high abundance.
54
Fe 53.94 amu 5.8 % rel. abundance
56
Fe 55.94 amu 91.8 % rel. abundance
Practice: Isotopes
An atom with 6 neutrons and a mass number of 13 is an isotope of which element?
Mg has three isotopes.
24
Mg is the most abundant (78.70%). Calculate the percentages of the other two isotopes. The exact masses are given below:
24
Mg = 23.98504 u
25
Mg = 24.98584 u
The Atom
2.
Calculate the average mass of chlorine to two decimal places given its two isotopes: chlorine-35 (34.97 amu, 76% abundance) and chlorine-37 (36.97 amu, 24% abundance).
The Atom
Calculate the average mass of chlorine to three decimal places given its two isotopes: bromine-79 (78.918 amu, 51% abundance) and bromine-81 (80.916 amu, 49% abundance).
Elements: Isotopes and Atomic Mass
Hydrogen exists as two naturally occurring isotopes 1H (1.00782504u) (99.9885%) and deuterium, 2H. What is the atomic mass of deuterium? The atomic mass of hydrogen is 1.00794u.
Elements: Isotopes
Bromine is a noxious fuming red liquid in its elemental form. Naturally occurring bromine has two stable isotopes
79
Br (78.918
u
) and
81
Br (80.916
u
). What are the relative abundances of these two isotopes?
Enter your answer as a percentage (ex. If the answer is 16.26%, enter 16.26 as the answer)
Elements: Isotopes
Nitrogen has two naturally occurring isotopes, nitrogen-14 (14.003074008u) and nitrogen-15 (15.0001088982). What is the percent abundance of each isotope if the standard atomic weight of nitrogen is 14.0067?
Elements: Isotopes
The transition metal rhenium has two stable isotopes. The atomic mass of rhenium is 186.2 g/mol. Given that 37.1% of natural rhenium is Re-185, what is the other stable isotope?
If the abundance of
6
Li (6.015121 amu) is 7.500% and the abundance of
7
Li (7.016003 amu) is 92.500%, what is the average atomic mass?
Boron has an average atomic mass of 10.81 amu. It has 2 isotopes:
11
B (relative abundance 80 %) and
10
B (relative abundance 20 %). If
11
B has an atomic mass of 11.01 amu, how much does
10
B weigh in amu?
Chlorine has two isotopes of interest. One has an atomic mass of 34.97 amu (relative abundance 75 %), while the other make up the remaining 25 % of this element. If Cl has an average atomic mass of 35.47 amu, what is the mass of the second isotope in amu?
B has two isotopes that are available naturally in meaningful abundance.
10
B (10.01 g/mol) has a relative abundance of 20 %, while
11
B (11.01 g/mol) has a relative abundance of 80 %. If you are given a 12 g sample, how many moles of
10
B are in the sample (answer in mol)?
Elements: Isotopic Mass
Copper exists as two naturally occurring isotopes
63
Cu (62.92960) (69.17%) and
65
Cu. What is the atomic mass of
65
Cu?
Elements: Isotopic Mass
Fe has three isotopes in relatively high abundance.
54
Fe 53.94 amu 5.8 % rel. abundance
56
Fe 55.94 amu 91.8 % rel. abundance
How would you determine the number of neutrons in an atom? Let's say the element is F.
Atom: Isotopes
Selenium has a number of isotopes associated with it.
76
Se = 75.92 amu rel. abundance = 0.094
77
Se = 76.92 amu rel. abundance = 0.076
Atom: Determining the mass
What is the total mass of a C atom?
Given the following information:
"The Periodic Table", image retrieved from Chemistry 2e (https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Chemistry2e-OP_QCzV58S.pdf) by Flowers, P
et al.
, is licensed under CC BY.
Atom: Isotopes and Atomic Weight
An ion with a -2 charge has a mass number of 52 and contains 26 electrons. Which element is this ion? Specify the isotope as well.
Carbon is made up of two stable isotopes,
12
C and
13
C.
12
C is the most abundant form (98.93%) with
13
C making up the remaining 1.07%. The
12
C nuclei is defined as exactly 12 amu, what is the weight of the
13
C nuclei? For this problem use the precise atomic weight of carbon, 12.0107
Atom: Calculating the Mass of One Isotope
Naturally occurring potassium contains two stable isotopes. The lighter isotope,
39
K ( 38.9637 amu) is the more abundant isotope, accounting for 93.26% of the nuclei. What is the weight of the heavier isotope,
41
K?
Boron (atomic weight 10.81) is made up of two stable isotopes,
11
B and
10
B. The boron-11 nuclei weighs 11.0093 amu and the boron-10 nuclei weighs 10.0129 amu. The percentage of
11
B and
10
B in naturally occurring boron respectively is,
How many protons does
13
C have?
An atom with 6 neutrons and a mass number of 13 is an isotope of which element?
How many electrons are there in
27
59
C
O
3
+
?
^{59}_{27}CO^{3+}?
27
59
C
O
3
+
?
Elements: Isotopes
Which of the following species has an isotope with a mass number of 42, 18 electrons, and an overall charge of 2+?