Atoms - Do they last forever or they decay?

[ModernArtist25]

When humans or animals die, do their atoms live on forever or do they eventually decay?

[Strange]

Most of the atoms carry on unchanged. There will be a few radioactive isotopes in there; those will decay to something else. Most famously, perhaps, carbon-14. That undergoes beta decay and produces nitrogen-14.

[Sensei]

As Strange pointed out,

Carbon-14 decay via path:

Carbon-14 -> Nitrogen-14 + e- + Ve + 0.156476 MeV

 

There is also Potassium-40 which decay via paths:

Potassium-40 -> Calcium-40 + e- + Ve + 1.31108 MeV
Potassium-40 -> Argon-40 + e+ + Ve + 0.482698 MeV
Potassium-40 + e- -> Argon-40 + Ve + 1.5047 MeV

 

Carbon-14 has half-life 5730 years.

Potassium-40 has half-life 1.248-1.251 billion years.

 

They are tiny tiny fraction of the entire body mass.

C-14 is 1 per trillion of Carbon atoms, which is 18.5% from body mass.

f.e. 80 kg = 80000 g * 18.5% = 14800 g / 12 g/mol = 1233.3 mol

C-14 with 1 ppt in entire Carbon has 1.234*10^-9 mol.

Edited September 20, 2016 by Sensei

[StringJunky]

When humans or animals die, do their atoms live on forever or do they eventually decay?

The half-life of a stable nucleon is speculated at 10³⁴ < 10³⁹ years.

 

 

The subsequent evolution of the universe depends on the possibility and rate of proton decay. Experimental evidence shows that if the proton is unstable, it has a half-life of at least 10³⁴ years.[30] Some of the Grand Unified theories (GUTs) predict long-term proton instability between 10³¹ and 10³⁶ years, with the upper bound on standard (non-SUSY) proton decay at 1.4 x 10³⁶ years and an overall upper limit maximum for any proton decay (including SUSY models) at 6 x 10³⁹ years.[31][32] Recent research showing proton lifetime (if unstable) at or exceeding 10³⁴-10³⁵ year range rules out simpler GUTs and most non-SUSY models.

Neutrons bound into nuclei are also expected to decay with a half-life comparable to that of protons. Planets (substellar objects) would decay in a simple cascade process from heavier elements to pure hydrogen while radiating energy.[33]

In the event that the proton does not decay at all, stellar objects would still disappear, but more slowly. See Future without proton decay below.

Shorter or longer proton half-lives will accelerate or decelerate the process. This means that after 10³⁷ years (the maximum proton half-life used by Adams & Laughlin (1997)), one-half of all baryonic matter will have been converted into gamma ray photons and leptons through proton decay.

https://en.wikipedia.org/wiki/Future_of_an_expanding_universe#All_nucleons_decay

Edited September 20, 2016 by StringJunky

[ModernArtist25]

So would you say that the atoms don't decay, they just convert into something else?

[StringJunky]

So would you say that the atoms don't decay, they just convert into something else?

Utimately, from that link, I think they degrade,and disperse as electromagnetic radiation. This is only theory though, based on what they understand now

[swansont]

The half-life of a stable nucleon is speculated at 10³⁴ < 10³⁹ years.

 

That's a free proton. A proton in a potential well should have an even longer lifetime aginst this decay.

So would you say that the atoms don't decay, they just convert into something else?

Spontaneously converting to something else is decay.

[StringJunky]

That's a free proton. A proton in a potential well should have an even longer lifetime aginst this decay.

Right.

[Bill Angel]

What about molecular hydrogen H2?

What would cause H2 to decay, assuming the molecules arn't bombarded with radiation or collide with each other?

Edited September 21, 2016 by Bill Angel

[StringJunky]

What about molecular hydrogen H2?

What would cause H2 to decay, assuming the molecules arn't bombarded with radiation or collide with each other?

Swansont said they would last a lot longer than free nucleons. As to why, that might be hinted by this snippet:

 

 

Protons and neutrons belong to a class of particles called "baryons," being composed of combinations of 3 more fundamental constituents known as quarks. Quarks are distinct from the other group of fundamental particles, the leptons, which incorporate electrons, muon and tau particles along with their corresponding neutrinos. Grand Unified Theories (GUTs) seek to join these two different classes together, allowing particles of one type to cross over to the other class. As a consequence, many GUT models predict that the proton or neutron may be unstable, with an ability to decay to light particles so as to decrease the net number of quarks in favour of producing more leptons. This would violate what is known as "baryon number conservation." The typical timescale for any one such decay to occur might be on the order of 1030 years or more… unimaginably long, far longer than the age of the Universe. However, by looking at similarly vast numbers of neutrons and protons, one might hope to see a few of these decays occur by chance. This is a very similar approach to detecting neutrinos, whose weak interactions make it essentially impossible to detect any particular one but where a handful amongst trillions passing through your detector might be seen.

 

http://snoplus.phy.queensu.ca/Nucleon_Decay.html

Edited September 21, 2016 by StringJunky

[Strange]

So would you say that the atoms don't decay, they just convert into something else?

 

 

Those that decay convert into something else. The others (which is pretty much all of them) stay as they are.

[swansont]

What about molecular hydrogen H2?

What would cause H2 to decay, assuming the molecules arn't bombarded with radiation or collide with each other?

 

 

From a nuclear standpoint, H2 is almost identical to a free proton. Atom/molecule potential well energy is measured in eV. Nuclear is measured in MeV.

[Fuzzwood]

But if you are wondering if some of your molecular makeup consists of atoms which once belonged to Jeanne d' Arc, Napoleon or John F. Kennedy, then yes.