Tuesday, January 5, 2016
CHEM 418 Nuclear Chemistry, Winter 2016: Lecture 2 Nuclear Properties
A discussion on systematics of nuclear properties are presented. Mass, mass excess, and mass distribution within the nucleus is presented. Mass excess data are used to calculate energies in decays. Equations for determining nuclear radii are provided. Models that are used to describe the stability of nuclei are introduced. Nuclear shapes and structures are introduced. PDF quiz 2 is due Wednesday 13 January.
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Where can I find the Chart of the Nuclides?
ReplyDeleteBagley 303
DeleteI really enjoy the lecture 2. I like calculating the Q value.
ReplyDeleteI sent the lecture 2 pdf quiz as an attachment through email.
Thank you
thanks for your PDF quiz submission
ReplyDeleteSo on lecture 2, I'm a little unsure of my final values of Q for the given reaction. I did my best to follow to form of each decay mode described in Lecture 2.
ReplyDeleteAs a way of checking myself I tried to balance each equation in terms of neutrons. However I ran into trouble with the decay modes, Positron Decay and Electron Capture.
2.4) 64Cu + e^- --Electr. Cap.--> 64Ni + V + Q
So 64Cu has 35 neutrons undergoes electron capture and 64Ni is formed now having 36 neutrons. Where does this extra neutron come from? Mass is conserved right haha?
2.5) 64Cu --Positron D.--> 64Ni + B^+ + V + Q
So for this example, 64Cu has 35 Neutrons undergoes Positron Decay and 64Ni is formed with 36 Neutrons. Again where does this extra neutron come from?
I know Electrons/Positrons are considerably lighter than Neutrons and Neutrinos have varying mass. So I find it hard to believe my equation is balanced.
Any help is greatly appreciated.
Great question!
DeleteFirst of all the extra neutron comes from the positron. In your examples the positron forms a neutron in the decay, in some cases with the emission of particles such as neutrinos and positrons. This decay will be discussed in more detail in the lecture on beta decay.
Yes the masses are varied. In fact for the Q values we use E=mc^2 to relate mass to energy. On page 4 of lecture 2 we have a relationship
1 AMU= 931.5 MeV. Decay energies are on the order of a few MeV, so this is well under an AMU. As you point out the masses are different, but the system is balanced if we include the energy. All this means in that the energy of the decay comes from the initial mass.
Okay, thank you for the explanation Ken.
DeleteQuiz #2 emailed
DeleteThanks for the quiz submission. Please see my reply
DeleteResubmitted my Quiz 2
Delete-Faruq
Lecture watched. Quiz sent through email. Thank you!
ReplyDeleteThanks for the quiz!
DeleteThanks for the quiz!
DeleteI emailed you my PDF quiz. This was an interesting lecture.
ReplyDeletequiz 2 submitted via email and one of the link provided on the quiz for q value did not open(nndc.bnl.gov).
ReplyDeleteThe link is on the assignment page, or just copy and paste the address on the quiz.
DeleteThe link is on the assignment page, or just copy and paste the address on the quiz.
DeleteFor calculating Q value in beta- decay vs positron decay:
ReplyDeleteI understand why positron decay is like having two extra electrons present and we took that into account in the Q equation. However, why exactly are we assuming that the electron in beta- decay is negligible (and therefore not necessary to put in the Q equation)? If each electron has a 0.511 MeV, then why shouldn't the Q for the 14C example given be: 3.0198 - (2.8634 + 0.511) = -0.3546 MeV?
Thank you.
This will be explained on more detail on the beta decay lecture.
ReplyDeleteAssume the emitted beta particle is part of the resulting nucleus, then its mass is considered. This is why there is a difference between electron capture and positron decay q values.
The PDF for Quiz 2 has been sent through Canvas email.
ReplyDeleteOn the Q-value calculator, what does the second number represent in the keV column?
PDF quiz received.
DeleteLecture viewed, and quiz submitted.
ReplyDeleteI was curious whether electronic structure stability influenced nuclear properties. This might be an obvious answer, but I couldn't really find a clear answer anywhere.
The only influence on electronic structure has been observed with electron capture, and to a very small effect.
DeleteQuiz 2 submitted via email in Canvas.
ReplyDeletePDF quiz 2 received. Thanks you.
DeleteLecture watched and quiz submitted via email!
ReplyDeletethanks for the response.
DeleteLate reply, still getting used to this online course...
ReplyDeleteAnother student and I had some trouble with the Q-Calculator. Had to use the q-values and calculate by hand, but it was a good practice.
The emerging properties of nuclei from the drop model were intriguing, interested in learning what the shell model predicts.
-Taylor Posey
Deletesorry about the problem with the q-value calculator. Good to know you did the exercise by hand.
Delete