foxstudy
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I don't understand. Do radioisotopes constantly emit radiation all the time or do they only emit radiation after each half life?? Confused.
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Crow_M
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They constantly emit radiation, the half life is basically the time that it takes for the mass to half, this means that it will be emitting whatever time of radiation all of the time, at some point it will be 1/2 of the mass.
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foxstudy
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(Original post by Crow_M)
They constantly emit radiation, the half life is basically the time that it takes for the mass to half, this means that it will be emitting whatever time of radiation all of the time, at some point it will be 1/2 of the mass.A
Ahhh and so why do we focus on 'half life' or the time it takes for half of the atoms in a radioisotope to decay rather than it's 'full life'?
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Crow_M
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(Original post by foxstudy)
Ahhh and so why do we focus on 'half life' or the time it takes for half of the atoms in a radioisotope to decay rather than it's 'full life'?
Because the radioactivity will never truly go away, it will go from (e. g.) 128,64,32,16,8,4,2,1,0.5,etc... Even if the number is really small it is still there, so the atom never truly stabilizes.

We take it's half life because we can have an idea of how fast it'll decay, this is helpful in medicine, you don't want a chemical decaying for years, you want its radiation to halve as fast as possible so it's less harmful.
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foxstudy
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(Original post by Crow_M)
Because the radioactivity will never truly go away, it will go from (e. g.) 128,64,32,16,8,4,2,1,0.5,etc... Even if the number is really small it is still there, so the atom never truly stabilizes.

We take it's half life because we can have an idea of how fast it'll decay, this is helpful in medicine, you don't want a chemical decaying for years, you want its radiation to halve as fast as possible so it's less harmful.
Why does the radioactive isotope never go away?
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Crow_M
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(Original post by foxstudy)
Why does the radioactive isotope never go away?
Because it keeps halving itself, even if you half a billionth of it it will still be there, but it'll be unnoticeable. (This is for A Level btw)
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foxstudy
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(Original post by Crow_M)
Because it keeps halving itself, even if you half a billionth of it it will still be there, but it'll be unnoticeable. (This is for A Level btw)
Ahh alright cheers.
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Pigster
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(Original post by foxstudy)
Why does the radioactive isotope never go away?
Take carbon-14 for an example (the radioactive one used for dating things).

If you had 14 grams of it, (i.e. 1 mol) that would be 6.02 x 10^23 atoms.

After 5,730±40 years (thank you wikipedia), you'd have half that: 3.01 x 10^23 atoms still waiting to decay.

After ten more half lives, you'd still have 2.94 x 10^20 undecayed atoms.

After another 60 or so half lives you'd be down to single figures. Do you fancy waiting half a million years or so?
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