Arrange the unstable isotopes in decreasing order based on the length of their half-life. carbon-14 (5.73 × 103 years) argon-39 (2.69 × 102 years) hafnium-182 (9 × 106 years) krypton-81 (2.29 × 105 years) calcium-41 (1.03 × 105 years) iron-60 (1.5 × 106 years)

a) argon-39 (2.69 × 102 years)  

b)carbon-14 (5.73 × 103 years)  

c)calcium-41 (1.03 × 105 years)  

d)krypton-81 (2.29 × 105 years)  

e)iron-60 (1.5 × 106 years)

f)hafnium-182 (9 × 106 years)

Explanation:

The most unstable isotopes would be the one which will have small half life. A half life depicts the time period in which a radioactive isotope would reduce to a quantity just half of its originals quantity. Thus isotopes with high half life period will take much longer time to reduce to their original quantity. Thus on arranging the given isotopes in decreasing order of stability, the following series is obtained –

a)argon-39 (2.69 × 102 years)  

b)carbon-14 (5.73 × 103 years)  

c)calcium-41 (1.03 × 105 years)  

d)krypton-81 (2.29 × 105 years)  

e)iron-60 (1.5 × 106 years)

f)hafnium-182 (9 × 106 years)

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