# Homework Help: Radioactive reactions -half-life Decay physics 30

1. Jan 1, 2008

### cathoderay

1. hi i would like to now how i could do this?
the question says:
iodine-131 is a radiactive element used in the medical diagnosis and treatment of thyroid problems. iodine-131 undergoes simultaneous beta and gamma decay and has a half-life of 8.00 days.

2.im ask to write the complete decay equation for iodine-131

3. i know the formula for the life time is N=No(1/2)^n and n=time after/half-life...T(1/2)
but im not sure if thats the equation to do the decay...
...or the complete decay equation they are asking for is a series of radioactive elements.. like the folowing
ex: 226 Ra--->222 Rn + 4 He
....... 88.............86..........2

if is as the example im not sure how to do it..could someone explain me how could i do it ? thanks

Last edited: Jan 1, 2008
2. Jan 3, 2008

### Shooting Star

Yes, this is what they are asking.

If an electron is emitted by the nucleus, what happens to the atomic number?

3. Jan 3, 2008

### daveb

Since they mention it's a beta emitter, but also mention the half life, I can see the confusion. Typically, in health physics and nuclear engineering, when asked for the decay equation for a radioactive element, it's asking for A(t) = A(0)exp(-lambda*t). However, it (i.e., the decay equation) is sometimes used in the second manner, as pointed out by Shooting star. I suppose it depends on the chapter of the book you're using. From the title of your post, it says half life decay, so I would go with the first

4. Jan 3, 2008

### Shooting Star

After reading the original post once more, I agree with user daveb. Sorry for misleading the OP a bit.