Errors in Ch 21 Self-Assessment Exercises

[Zellmer, Robert]

A fellow student contacted me about problems with three SAEs in Ch 21.

Section 21.1:

SAE 21.4

What particle is produced during the following decay process? Mn-56 decays to
Fe-56

56                56            0
     Mn  --->       Fe  +      e
25                26           -1

A beta particle is ejected from the nucleus as a neutron converts into a
proton and electron (which is ejected from the nucleus).  The electron
in this case is called a beta particle.

Answer (a) is beta particle (β-)

The answer given when you click on the answer box is "a) alpha particle, (β-)".
It's not "alpha" but "beta".


Section 21.2:

SAE 21.7

The final two steps in the decay chain for uranium-238 are:

            Bi-210  --->  Po-210 --->  Pb-206

Lead-206 is a stable isotope. What are the radioactive decay processes for

these two steps?



The answer given is:



e. electron capture followed by alpha emission



There is a misprint in the explanation.



The answer should be:



e. beta emission followed by alpha emission


SAE 21.8

Which of the following statements about the stability of nuclides is false?



The answer given is:



e. A nucleus that decays via electron capture has a neutron-to-proton ratio

that is lower than expected for stability.



This is true.



The correct answer should be (the false statement):
a. Nuclides in the belt of stability always have the same ratio of neutrons
to protons". It actually increases from around 1 for lighter nuclides to 1.5
as the nuclides get larger and heavier.


Dr. Zellmer

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