Problem: Which of the following isotopes would you expect to be stable?a. 40Cab. carbon-12c. 208Pbd. uranium-235e. 208Po

FREE Expert Solution

We are being asked to identify the isotope that is expected to be stable


Recall that the stability of an isotope depends on the ratio of neutrons to protons (N/Z). This means for stable isotopes with:

• Z ≤ 20; the N/Z ratio should be equal to 1.0

• 20 < Z ≤ 40; the N/Z ratio should be equal to 1.25

• 40 < Z ≤ 80; the N/Z ratio should be equal to 1.50

• Z > 81; the stable nuclide does not exist


Also recall that the atomic mass is the sum of protons and neutrons and the atomic number tells us the number of protons.


  • Atomic number = # protons 
  • Atomic mass = # protons + # neutrons


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Problem Details

Which of the following isotopes would you expect to be stable?

a. 40Ca

b. carbon-12

c. 208Pb

d. uranium-235

e. 208Po

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