Isotope Questions

Close window when finished.

Question 1:

Magnesium has three isotopes, Mg−24, Mg−25, and Mg−26. The percentage of each in order is 78.70%, 10.13%, 11.17%. Calculate the relative atomic mass of Magnesium.

 

 

 

The formula given in the Isotope page can also be used to calculate the percentage composition of an element’s isotopes.

 

Question 2:

Calculate the percentage composition of boron given that the relative atomic mass of boron is 10.8 and the mass numbers of the two isotopes are 10 and 11. (Hint: You will need to express the percentage of one isotope in terms of the percentage of the other.)

 

Question 3

Fill in the blanks for these neutral atoms.

Element Name

Atomic Number

Number of Protons

Number of Electrons

Positive Charge on Nucleus

Mass Number

Number of Neutrons

Carbon

        

12

  
 

10

        

10
   

1

    

1

  
     

3

    

4
       

2

4

  

Calcium

          

20
 

11

      

23

  

 

Question 4:

Atoms of a certain isotope have 73 neutrons and a mass number of 123.

(a) What is the atomic number?

(b) How many electrons are there?

(c) What is the name of the element?

(d) What is the nuclear charge?

 

Question 5:

Which of the following are isotopes of each other?

(a) An atom with 17 protons and 18 neutrons?

(b) An atom with atomic number 16 and atomic mass 32?

(c) An atom with atomic number 16 and 18 neutrons?

(d) An atom with 16 protons and 18 neutrons?

(e) An atom with 17 protons and 20 neutrons?

(f) An atom with atomic number 16 and atomic mass 33?

(g) An atom with 15 protons and 16 neutrons?

 

Question 6:

A naturally-occurring sample of element X is found to contain 81.8 per cent X-10 (ie, element X with a mass number of 10) and 18.2 per cent X-11. Calculate the apparent atomic mass of this naturally-occurring sample of element X.

 

Question 7: 

Copper is listed on the periodic table as having a relative atomic mass of 63.55. Reference books indicate two isotopes of copper, with relative masses of 62.93 and 64.93. Find the percent abundance of each isotope.

 

Question 8:

Element E occurs in two isotopes. 15% of all atoms of E have a relative atomic mass of 51.05 and the rest a relative atomic mass of 52.05. What is the average relative atomic mass for the element E?

 

Close window to continue.