Gamma rays, protons, neutrons

[Ice-cream]

I am studying radioactive decay at the moment, and when it comes to writing equations with alpha, beta particles, positrons, protons, neutrons and gamma rays, I don't understand under what circumstances an element would emit gamma rays. (i mean, i know for eg. alpha particles are emitted when an element has too many protons and neutrons) What about protons? Neutrons? THanx

[swansont]

I am studying radioactive decay at the moment, and when it comes to writing equations with alpha, beta particles, positrons, protons, neutrons and gamma rays, I don't understand under what circumstances an element would emit gamma rays. (i mean, i know for eg. alpha particles are emitted when an element has too many protons and neutrons) What about protons? Neutrons? THanx

 

Gammas are emitted when the nucleus is in an excited state. The nucleus de-excites by emmitting a gamma.

 

Neutron emission can happen with an excited nucleus that has an excess of neutrons - this typically happens after a beta-minus decay that leaves the daughter in an excited state. (This is an important neutron source in nuclear reactors that use thermal neutrons)

 

Proton emission isn't something with which I am familiar, but I imagine it could happen in a way that mirrors the neutron emission - excited nucleus after a beta-plus decay.

 

Neutron and proton emission can also occur in induced reactions.

[Gilded]

Yum yum, questions about radioactive decay.

 

"I don't understand under what circumstances an element would emit gamma rays."

 

When a nucleus is excited (for example, when a decay happens), it emits a gamma ray. And I'd imagine the more excited it is, the less is the gamma ray's wavelength.

 

And about the other decays, there are a lot of those. I personally find EC (electron capture) and SF (spontaneous fission) the most interesting.

 

In an EC, the nucleus captures one of the electrons surrounding it, which leads to a decrease of charge. Also, when this happens, an x-ray photon is emitted.

 

In an SF, the nucleus is just too unstable, going through fission without the affection of any outer particles or forces. For example, a fermium-256 nucleus has a 8.10% chance of decaying through alpha, and a 91.90 chance of decaying through spontaneous fission. Yipes. As you might imagine, it's not too healthy to eat this sort of isotopes, as fission happening inside your body isn't too nice (when measuring an equivalence dose of ionizing radiation, heavy multi-atomic particles have a Q factor of 20).

 

And as for the neutrons and protons, there's the beta- (electron emission) and beta+ (positron emission). In a beta- decay, the weak nuclear forces cause a neutron to convert into a proton, an anti-neutrino and an electron. In beta+, same happens with a proton, that converts into a neutron, a neutrino and a positron. The neutrons and protons remain in the nucleus, but electrons and positrons and neutrinos and anti-neutrinos leave the atom. As you might know, the positron doesn't usually travel far, since immediately it encounters an electron... BOOM. Matter-antimatter annihilation, transforming the two particles into gamma photons.

 

I'm hoping that even some of this information was helpful.

 

Edit: Oh, swansont answered the neutron/proton thingie. Yes, I forgot to mention that they don't always stick with the atom's nucleus.

 

Edit2: Dammit, forgot to mention that sometimes a neutron emission is even stated as a nucleus' official decay mode, which is the case with for example H-4 emitting a neutron becoming H-3 (tritium). This is quite rare though.

 

Edit3: Yay for me. Should have really double checked the post BEFORE posting. Yeah, I forgot to mention too that sometimes a double decay happens which is the case with for example beryllium-6 emitting two protons to become helium-4.

 

Edit4: Lol, forgot to mention about isomeric transition, where a nucleus of relatively long metastable state becomes stable, emitting nothing but a gamma ray. Such is the case with technetium-99m becoming technetium-99. Its metastable state lasts about 6 hours, which makes it a good isotope for medical research.

[jsatan]

And if I was asked this question 3 years back I could tell you everything about it.

I was in some ways a little xpert in that subject. but now as time goes by my memory goes as well.

 

but yeah glide seems to have it right.

[swansont]

Edit4: Lol, forgot to mention about isomeric transition, where a nucleus of relatively long metastable state becomes stable, emitting nothing but a gamma ray. Such is the case with technetium-99m becoming technetium-99. Its metastable state lasts about 6 hours, which makes it a good isotope for medical research.

 

The nucleus can still be unstable after IT. In your example, the Tc-99 ground state undergoes beta-minus decay.

[Gilded]

D'oh. I meant stable in the aspect of not being in excited state, but in ground state, as you pointed out. The fever aftermath does magical things to writing things.