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 what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"There are different types of radioactive decay, which affect the chemistry of an element differently. The more protons there are (as well as neutrons) the stronger the nucleus tries to hold together (and these protons and neutrons are 'transforming' into each other which contributes to this strong force). For alpha decay, a helium atom is ejected from the nucleus. Beta negative: a neutron is transformed into a proton and an electron. For beta positive: a positron is emitted (an electron with a positive charge)."
"The joy of radioactivity. An atomic nucleus will always try to achieve stability if it has too many protons (more than 83), too few protons, or too many neutrons. Ironically, neutrons themselves are unstable and constantly switch back and forth between neutrons or protons. So in order to achieve stability they must eject neutrons/protons if they have too many protons, an event called alpha decay. Transforming neutrons into protons, if it's got too many neutrons, called beta- decay, this has the added benefit of emitting an electron and neutrino. Then there's beta+ decay if a nucleus has too few neutrons, by converting protons into neutrons, and releasing a positron and neutrino. Finally, if the nucleus still has excess energy, it is emitted in the form of gamma rays, known as gamma decay."
"Beta- decay turns neutrons into protons and beta+ does the opposite. They do this because a nucleus is trying to maintain a stable ratio of protons to neutrons, and this is some of the couple ways that it can be done."
Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"Nothing, this was my favorite part of general chemistry."
"This class suddenly seems to be getting into chemistry."
"Honestly its hard to pinpoint one part that's confusing, it's all rather confusing at this point."
"What is electron capture? Why can there be more neutrons but never more protons?"
"I don't understand how the protons change into neutrons or neutrons change into protons."
"I understand the 'sticky' strong force that keeps protons and neutrons together and thus a nucleus stable, but it's kinda weird to all of a sudden be talking about a totally different kind of force."
Explain what a "nucleon number" is, and/or describe how to calculate it for a nucleus.
"I don't know what nucleon number is or how to calculate it."
"It's the total number of protons and neutrons in the nucleus of an atom."
Identify the processes that increase, decrease, or do not change the number of protons in the nucleus.
(Only correct responses shown.)
α decay: decrease. [68%]
β– decay: increase. [62%]
β+ decay: decrease. [71%]
electron capture: decrease. [32%]
γ decay: does not change. [59%]
Identify the processes that increase, decrease, or do not change the number of neutrons in the nucleus.
(Only correct responses shown.)
α decay: decrease. [62%]
β– decay: decrease. [65%]
β+ decay: increase. [68%]
electron capture: increase. [42%]
γ decay: does not change. [56%]
Identify the processes that change a proton to a neutron, or change a neutron to a proton in the nucleus.
(Only correct responses shown.)
α decay: no p/n conversion. [53%]
β– decay: n → p. [68%]
β+ decay: p → n. [68%]
electron capture: p → n. [44%]
γ decay: no p/n conversion. [56%]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Studying or not studying, reading or not reading, same scores on quizzes. I would prefer more explanations before I read." (Let's try testing one more independent variable--asking questions in office hours, or not asking questions in office hours.)
"What would you say is the most important equation or equations to focus on for our midterm next week?" (All of them. Or none of them. What I mean to say is that you should be able to explain how to use equations to explain your answers, as I already know you can all plug-and-chug equations.)
"This stuff is nonsense. Yet very fun to think about."
"Thanks for your diligence for all your help."
"I'm working 40 hours a week I think work and school are both getting difficult. I'm trying my best to push through and earn a good grade in this class."
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