How do I determine the half life of an alpha particle?

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Discussion Overview

The discussion revolves around determining the half-life of a helium nucleus and its relationship to the half-life of its constituent particles, as well as the stability of helium as an atom and nucleus. Participants explore concepts in nuclear chemistry, including the stability of various nuclei and the implications of neutron half-life.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the half-life of a helium nucleus can be derived from the half-lives of its constituent particles, specifically neutrons and protons.
  • Another participant asserts that the helium nucleus and atom are stable, emphasizing that the stability of an atom is determined by its nucleus.
  • Some participants clarify that the standalone neutron has a half-life of about 15 minutes, but this does not directly relate to the half-lives of various nuclei.
  • There is a discussion about the existence of unstable atoms with stable nuclei, with beryllium-7 cited as an example.
  • Participants inquire about the characteristics of unstable atoms with stable nuclei, leading to a mention of dysprosium-163 as a potential example.
  • One participant expresses uncertainty about the existence of other examples beyond dysprosium-163.
  • There is a debate regarding the terminology used to describe stable atoms with unstable nuclei versus unstable atoms with stable nuclei, with clarifications provided on the definitions.
  • The concept of ion stability versus neutral atom stability is introduced, noting that ions can exhibit different stability properties.

Areas of Agreement / Disagreement

Participants generally agree on the stability of the helium nucleus and atom, but there is disagreement regarding the relationship between neutron half-life and the half-lives of other nuclei. The discussion also reveals competing views on the definitions of stable and unstable nuclei and atoms.

Contextual Notes

Participants express uncertainty about the existence of multiple examples of unstable atoms with stable nuclei and the implications of electron capture on stability. The discussion does not resolve the complexities surrounding these definitions and relationships.

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I am fairly new to nuclear chemistry and I was just curious as how to find the half life of a helium nucleus. Would it be the same as finding the half life of 1 neutron x2 and 1 proton x2? Or is this the completely wrong way to do this. Also would the half life be the same as a helium atom or completely different? This isn't for any homework assignment, I am just curious.
 
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Helium nucleus is stable, also helium atom is stable. Stability of atom is given by stability of its nucleus.

Standalone neutron half life is 15 minutes and it is not related to half life of various nuclei. There are effects in nucleus which "stabilize" the neutron.
 
mpv_plate said:
Helium nucleus is stable, also helium atom is stable. Stability of atom is given by stability of its nucleus.
Not completely. There are many unstable atoms with a stable nucleus, starting with beryllium 7, and a few stable atoms with unstable nucleus.
mpv_plate said:
Standalone neutron half life is 15 minutes and it is not related to half life of various nuclei.

It is not unrelated, but the half-lives of various nuclei are not given by neutron lifetime. Rather, neutron is one nucleus of many, and the rules giving nucleus lifetime apply to free neutrons among others.
 
a few stable atoms with unstable nucleus.
I can't think of one, could you give an example?
 
snorkack said:
There are many unstable atoms with a stable nucleus, starting with beryllium 7
All nuclei where electron capture is the only possible decay process, but I think those are quite rare.
a few stable atoms with unstable nucleus.
I am interested in an example here, too.

The helium 4 nucleus is stable if the proton is stable. If it is not, the individual nucleons in the nucleus can decay, and the nucleus has a lifetime comparable to the lifetime of protons (more than 10^30 years). The electrons are not relevant here.
 
Bill_K said:
I can't think of one, could you give an example?

Dysprosium 163.

Not sure whether others exist or whether Dy-163 is the only one.
 
snorkack said:
Dysprosium 163.

Not sure whether others exist or whether Dy-163 is the only one.

One isn't "many".

What makes Dy163 an "unstable atom with a stable nucleus"? What is the characteristic of such a thing?

Zz.
 
ZapperZ said:
One isn't "many".
No, but "a few" includes one.
ZapperZ said:
What makes Dy163 an "unstable atom with a stable nucleus"? What is the characteristic of such a thing?

Vice versa. It is a "stable atom with unstable nucleus".

Beryllium 7 is an "unstable atom with stable nucleus". Its nucleus is stable because it has no way to decay in the absence of available electrons. The atom is unstable because if an electron is around the nucleus, it is captured.
 
Nice, I thought of that option, but I did not know that such a nucleus exists.

ZapperZ said:
What makes Dy163 an "unstable atom with a stable nucleus"? What is the characteristic of such a thing?
They ##\beta^-## decay energy is not sufficient to produce a free electron. If the inner shells are free, on the other hand, the nucleus can do a ##\beta^-## decay and produce a bound electron. Therefore, the atom is stable, but the nucleus (without electrons) is not.
 
  • #10
It is true that there are ions that have different stability properties than neutral atoms. It is not only true, it's interesting.

Now, read the OP again, and tell me that this is helpful.
 

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