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Competency #5

• Analyze atomic structure in terms of the Bohr model

Learning Objectives b & c

• b. Calculate the number of neutrons for the most common isotope of an element using the periodic table
• c. Explain how one isotope differs from another

Question

Write down your answer to the following question:

The mass number for the most common isotope for an element can often but not always be found by rounding the atomic mass found on the periodic table to the nearest whole number. Using this method, determine the number of neutrons that you would be most likely to find in an aluminum (Al) atom.

One exception is nickel (Ni). Based on the periodic table, you would expect 59 to be the mass number of the most common isotope. However this isotope is not even listed among the most common isotopes observed:
nickel-58: 68.3%; nickel-60: 26.1%; nickel-61: 1.13%; nickel-62: 3.59%; nickel-64:0.910%.

(based on data from http://presolar.wustl.edu/ref/IsotopeAbundanceTable.pdf)

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