20130430

Online reading assignment: radioactive decay modes

Physics 205B, spring semester 2013
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on radioactive decay modes.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"I found it very interesting that the nucleus of the atom that is decaying simply want to be more stable and changes to become that and therefore emits some particle."

"It was interesting to read about the strong force and that it is responsible for holding the nucleus together."

"That protons can become neutrons."

"I like how this lecture seems kinda like chemistry."

"I find it interesting that we are learning the same thing in my chemistry class!"

"I found the PET scan image interesting and how when sugar molecules are ingested they can be configured to be metabolized only in certain tissues, and will then give off positrons in these regions as the fluorine decays."

"The cloud chamber demonstration was awesome. It was cool to visually see a half-life undergoing."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The concept of stability has always been confusing to me, I know it seems simple with just certain numbers of protons and neutrons but i just get confused."

"Electron capture is a little fuzzy for me."

"I can't figure out what other particles are created when a proton turns into a neutron, and when a neutron turns into a proton."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I am confused on why 83 is this magic number of instability and why atoms with more protons than that will be unstable" (Actually, nobody seems to know from first principles why this number is so special--but taken that 83+ protons cannot be possibly be stable in a nucleus, nuclear physicists (and yes, nuclear chemists as well) come up with models that are consistent with this real-world observation.)

"I was a little confused that there are so many types of decay." (Because there are so many ways a nucleus can be unstable (having the wrong number of protons and neutrons), and many ways a nucleus can best reach a more stable combination of protons and neutrons within it.)

"If found it confusing to understand how proton turn into neutron and vice versa. I understand that a neutron will decay into a proton but I don't understand how a proton turns into a neutron." (Protons don't really want to be changed into neutrons, but can be forced to do so if it is for the benefit of the making the nucleus more stable. On the other hand, isolated neutrons outside of a nucleus will eventually turn back into protons, as there is no need to keep being a neutron.)

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