Question on Isotopes

[Irish Caesar]

Wiki has it unstable regarding beta- decay with a halflife of 8hours.

Ah, okay... I think that's a metastable state. I have that, but also that .012% of natural tantalum is 180, and it has a half-life of 1.2x10[super]15[/super] years.

Yes. Eventually a stable isotope can be the result of decay.

It's just that it might be a completely different element.

A stable isotope is always the result of a decay chain, eventually... sometimes that takes an awful long time, of course. It's almost always a different element in the end.

wait wait wait.....how are isotopes formed in the first place, I know its just loosing a subatomic particle, but how can one lose a subatomic particle?

They get formed in stars and supernovae from fusion reactions... the unstable ones decay from there, the stable ones don't.

 

[ori]

half-life is very predictable - if you have an isotope with a half-life of 1 hour and you start out with 100 nuclei of this isotope you will have only 50 left after an hour and 25 left after 2 hours etc. What is unpredictable is which of these nuclei will decay at what time point...

As for the radiation burn:
any process that kills cells so quickly that they cannot enter the programmed cell death (called apoptosis) will lead to a different form of cell death (necrosis) which leads to the formation of cell debris which in turn causes the organism to attempt to remove it by means of certain immune cells. This response includes an increase in blood flow to the affected area (noticed as a heated tissue which turns red) as well as the removal of any dead and some healthy tissue which, if extensive, can result in scarring. Now it does not really matter whether this massive cell death is caused by heat, cold, acid, base, radiation or any other means - the essential reaction which looks like a burn is always the same: lots of cells die, then the organism recruits immune cells to remove the dead cells leaving a vacant space which is filled with scar tissue. Not everything that looks like a burn is actually heat induced...

 

[Irish Caesar]

Also, to my knowledge, are half-life unpredictable?

Unpredictable... how?

As ori said, you can't really predict when a certain nucleus will decay (although it tends to follow a Poisson distribution...).

You can, however, calculate the half-life given the energy of the decay radiation. But since we've got tables of half-life data, there's no great need to do that (but it's nice to know we can!).

 

[Harbringer]

What do you mean by immune cells?

Im also wondering how fusion releases energy? I read an article on it and it just confused the hell out of me....

 

[ori]

What do you mean by immune cells?

cells of the immune system - essentially those cells in any higher developed organism that fulfill the role of getting rid of any foreign material and cells - this includes cell debris... There are specialized cells that remove such material by eating and digesting them...

 

[brennan]

What do you mean by immune cells?

Im also wondering how fusion releases energy? I read an article on it and it just confused the hell out of me....

In fission energy is released as large, unstable atoms decay into smaller, more stable atoms. In Fusion energy is released by squashing small, but stable atoms into larger atoms which are, if you like, more stable in that they require less energy to bind the nucleons all together.

 

[MrCynical]

What do you mean by immune cells?

These are specialised cells that basically destroy foreign or otherwise undesirable material in the body. They're termed "immune" because of their role in destroying bacteria, viruses and so on, protecting the body from disease. However they also mop up stuff like dead cells and debris which, while it was once part of the body, is no longer useful. In a radiation burn radicals generated by ionizing radiation react with, and hence damage cells (in particular they can damage DNA). The "burn" is simply the way the body reacts to clean up the damaged or destroyed cells.

Ionising radiation can in some cases burn directly. Gamma radiation is just high frequency EM radiation, and when absorbed by the body can be converted into heat. The rise in temperature is then responsible for the damage cells.

Im also wondering how fusion releases energy? I read an article on it and it just confused the hell out of me....

OK, I'll try and keep this simple. The nucleus of an atom is held together by the strong nuclear force. The amount of energy required to pull a nucleus apart depends on the exact numbers of protons and neutrons in it, and is known as the nuclear binding energy. Owing to the way the way the competing electromagnetic and strong nuclear force work out, very small nuclei like hydrogen have very low nuclear binding energies. Up to a certain point, as the nucleus increases in size, so does the nuclear binding energy. For common isotopes it reaches a maximum at Iron-56. After that it gradually decreases as the nucleus increases in size, so Uranium-235 for example has a somewhat lower nuclear binding energy. There's a graph of this here which might make things a bit clearer.

The point is that if I stick two small nuclei (e.g. two hydrogens or two deuteriums) together, I'll get a larger nucleus, with a higher nuclear binding energy per proton and neutron than I had when they were seperate. This extra energy is released.

If I go to isotopes heavier than iron, fusion no longer gives out energy. The nuclear binding energies are now lower as the elements get heavier. I'd have to put in extra energy to stick the nuclei together. However, I can now now use the reverse process. Split a very heavy nucleus (e.g. U-235) into two lighter nuclei which have higher nuclear binding energies, and again, that extra bit of energy is released.

So loosely speaking, very small nuclei are less "stable" than moderate size nuclei. Very heavy nuclei are also less "stable" than moderate size nuclei. Going from a less stable to a more stable state will release energy. The turning point is at about iron-56 which you can't get energy from using fission or fusion.

 

[Perfection]

I'm no expert at this crap, but here's a couple quickies.

2: There are three types of radiation: Alpha radiation: atom looses two protons and two neutrons, effectively a helium core. Beta radiation is an electron emitted from a neutron, turning it into a proton (neutrons are slightly heavier than protons). Gamma radiation: electromagnetic waves.

There are others too, those are just the most common.

A stable isotope is always the result of a decay chain, eventually... sometimes that takes an awful long time, of course. It's almost always a different element in the end.

Well, not a single, but often many!

 

[Padma]

I might point out that the energy required to cause fusion is huge. Of course, the energy released by the fusion is even greater.

In "thermonuclear" weapons, a 'small' fission reaction is used to trigger the fusion.

 

[Irish Caesar]

Well, not a single, but often many!

Wha?

Or were you just clarifying that a decay chain was many decays?

 

[Perfection]

Well, decay chains often yield many products.

 

[Leifmk]

I might point out that the energy required to cause fusion is huge. Of course, the energy released by the fusion is even greater.

...as long as you're fusing elements lighter than iron; past that, fusion costs more energy than it releases. Thus, heavier elements pretty much aren't produced under normal circumstances even within the largest stars; you need even more energetic environments for that (namely supernovae).

In "thermonuclear" weapons, a 'small' fission reaction is used to trigger the fusion.

What you need is basically immense heat/pressure; an abundance of free neutrons helps a lot as well. The easiest way to get this is indeed to set off a fission bomb.

 

[Millman]

To answer your question you might need days/weeks/months/years to know what you might want to know about isotopes.

There's so much out there that what you are basically asking is what High School students and College students are doing now. You simply have to study what interests you. This stuff doesn't interest me so I took up Chess and Games instead.

What you generally need to know is that this law of science might you are asking has so many different principles it's hard to know it's true meaning.

It is possible to be 'unclear' about the results because we haven't studied every process but it's good to know it works somehow and you have an interest in finding that out.

Was that what you wanted? It seems like you wanted to know it all at once.

 

[Padma]

...as long as you're fusing elements lighter than iron; past that, fusion costs more energy than it releases. Thus, heavier elements pretty much aren't produced under normal circumstances even within the largest stars; you need even more energetic environments for that (namely supernovae).

100% agree! MrCynical pointed that out a few posts earlier, and I just didn't bother to reiterate it.

 

[Harbringer]

To answer your question you might need days/weeks/months/years to know what you might want to know about isotopes.

There's so much out there that what you are basically asking is what High School students and College students are doing now. You simply have to study what interests you. This stuff doesn't interest me so I took up Chess and Games instead.

What you generally need to know is that this law of science might you are asking has so many different principles it's hard to know it's true meaning.

It is possible to be 'unclear' about the results because we haven't studied every process but it's good to know it works somehow and you have an interest in finding that out.

Was that what you wanted? It seems like you wanted to know it all at once.

Yet somehow everybody else made it perfectly clear to me in a few posts? Look I don't mean to be a jerk but why even bother posting if your not going to contribute?

 

[Riffraff]

Yet somehow everybody else made it perfectly clear to me in a few posts? Look I don't mean to be a jerk but why even bother posting if your not going to contribute?

I really don't think that everything should be perfectly clear at this level yet

edit: not that I know if it ever does become perfectly clear..