Questions and Answers on Nuclides

I try to keep questions submitted by groups as the are. Unclear or trivial questions are not replied. Reply has not been proof read.

Q
Stability and half life
The general explanation for radioactive decay is that the nuclide is trying to become more stable. How does the radioactive decay help make the nuclide become more stable? If the products of the nuclide are still unstable and decay again, then its half-life should be longer then the half life of the previous nuclide. (since the product is more stable) Yet there are many cases where this does not happen. Why would a nuclide then undergo decay if the products seem less stable than the original nuclide? Is the half-life of a nuclide an accurate way to predict its stability? Why or why not?
A
Based on my first intuition, I agree with you that half life should be an indication of stability. However, reality is more complicated than a theory. The term stability here indicates total energy of the system. Lower enrgy is more stable, and changes usually release energy.

There is another kinetic factor regarding the rate of change. This is related to the barrier to resist change. Half life is a measure of rate of change.

Q
Magic numbers
What is the explanation for the existence of magic numbers? Why do they exist?
A
Nuclides with certain numbers of neutrons and protons seem particularly stable, as we have observed. Then, there is a quantum mechanics trying to explain the structure of the nuclei. The energy levels suggest that nuclei with these numbers of protons and/or neutrons should be more stable. Thus, these numbers are called "magic numbers". As to how and who called it first, I do not know.

Q
Frozen State
Why is a nuclide as a whole considered as a frozen energy state? Why "frozen"?
A
Energy in the form of electromagnetic wave travels at the speed of light. When a bundle of energy freeze to form a nuclide, its there for an indefinite period of time. I used the word frozen to reflect this aspect.

Q
Light-weight nuclide
Why are nuclides with Z <= 20 considered light-weight nuclides? Why 20 but not 25 or any other numbers?
A
Since 20 is a magic number, I used this number to draw a line, which I must have because of space limitation for printing.

Q
Abundance of Elements
The figure on page 185 of the notes shows the atomic abundance of elements in the inner solar system excluding the sun. How would these types of measurements be made for other planets such as Mercury and Venus without taking actual samples? Is there some mechanism to analyze the atomic spectra emitted from those planets?

Why are the elements with smaller atomic numbers more abundant?

Why aren't more heavier nuclides created for testing the large magic number but just up to 112?
A
Abundances of elements are estimated from many sources of data, from geological survey, statistical analysis, to atmosphere studies. The accuracy is low, but they are a set of useful information.

The diagram is plotted on a log scale, and the height differ by a magnitude per division. These are facts, and we have no explanation for why.

Elements with atomic number greater than 92 are all man made. We shall discuss them in Nuclear Reactions.

Q
Why research?
There seems to be an endless quest to continue to find new and heavier elements with seemingly infinitesimally small half-lives. What is the motivation behind this continued reasearch? Is there any application in which these gigantic particles can be used? Even if they did discover a new stable element at 126 as Seaborg predicited, how would that be applied to anything?

What else is better to do than trying to make something new?

Q
SiO2 abandance
What processes made it possible for silicone and oxygen to be the most abundent elements in Earths crust?
A
The Earth formation process made SiO2 abundant.

Q
Stability of D and T
Why Deuterium is more stable than Tritium? Tritium has 2 neutrons, which is a magic number, while Deuterium only has odd number of neutron and proton.
A
We only know that D is not radioactive, while T is. As to why, I don't know, but I am glad you ask.

Q
Mass excess and decay energy
How does mass excess relate to decay energy?
A
The direct relationship is not interesting, but the mass excess'es of related nuclides are used to evaluate decay energy.

Q
Spin 1/2
On page 182 of the course notes, it says that free nucleons have spin. What does it mean by spin?
A
The electron has a spin of h/2p>. There are two states of these particles, and the two states are +h/2p>, and -h/2p>. When they are placed in a magnetic field, the spin effect is seen. The unit for the spin is h/2p>.