Isotopes
Chapter 2
University of Arkansas at Little Rock
Dr. Robert Belford




Question 1
Ytterbium-169 (16970Yb is a radioactive isotope used in cerebrospinal fluid studies of the brain. Identify how many protons, neutrons and electrons are present
(A)  70 protons,99 neutrons & 70 electrons
(B)  99 protons,70 neutrons & 99 electrons
(C)  70 protons,99 neutrons & 99 electrons
(D)  169 protons,99 neutrons & 169 electrons
 

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Question 2
Which species has 48 electrons
(A)  11850Sn+2
(B)  6831Ga
(C)  11850Sn+4
(D)  11248Cd+2
 

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Question 3
The average atomic weight of copper is 63.5 amu. Cu has 2 naturally occuring isotopes. One has a weight of 62.9amu and an abundance of 69.1%. What is the atomic weight of the other isotope?
(A)  63.2
(B)  63.8
(C)  64.1
(D)  64.8
 
Hint

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Question 4
Silver has two isotopes, one of mass 106.9 amu and one of mass 108.9amu. What is the fractional abundance of the lighter isotope?
(A)  .5160
(B)  .4824
(C)  .2763
(D)  .6743
 
Hint

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Question 5
An unkown element is found to have 3 naturally occuring isotopes with the following masses and % abundance; 35.9675amu(.337%),37.9627amu(0.063%) & 39.9624amu(99.600%). Which of the following is the unknown element?
(A)  K
(B)  Cl
(C)  Ca
(D)  Ar
 

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Question 6
Strontium-90 (90Sr) was released into the atmosphere during the Chernobyl nuclear accident. This isotope has
(A)  90 protons, 38 neutrons & 90 electrons
(B)  52 protons, 38 neutrons & 52 electrons
(C)  38 protons, 52 neutrons & 38 electrons
(D)  38 protons, 90 neutrons & 52 electrons
 

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