# Homework Help: Homework Question - Beta and Alpha decay

1. Apr 5, 2014

### LotusTK

Hi, i am new here. Thought it would be good to sign up as i have just started hitting the books in preparation for my AS Level exams. So this is my first question.

I think i may have done this question correctly, but i was just seeing what other people think as i am not 100% sure about it.

Question:

A nucleus of the radioactive isotope of bismuth Bi (213) and (83) emits a beta particle, then an alpha particle, then another beta particle before it becomes stable.

a) Show that the stable nucleus formed is a Bismuth isotope

My Attempt at it

Bi (213) (83) → Bi (213) (84) I have added one to the proton number, because in beta decay, a neutron turns into a proton, so the nucleon number remains the same, but the proton number goes up by 1.

Then for Alpha, it becomes Bi (209) (82). I have taken 4 from the nucleon number and 2 from the proton number because an alpha particle consists of 2 protons and 2 neutrons.

Then after the second beta decay i ended up with Bi (209) (83).

Is this correct?

2. Apr 5, 2014

### Curious3141

Looks good, but I'm not sure whether they're expecting you to write step by step proper nuclear reactions (including the electrons and antineutrinos and the alpha particles ).

3. Apr 5, 2014

### Staff: Mentor

I agree with the numbers, but the symbols of the intermediate nuclei are not "Bi".

4. Apr 5, 2014

### LotusTK

Thanks for the replies.

Curious3141, i dont think you do have to, but i know how to if i were to be asked in an exam. Just write B (0) (-1) add the anti neutrino (the v with the line above it) to the beta decay, and fore alpha, write the alpha symbol with (4) (2).

mfb, I just used "Bi" as that was the element quoted in the question. I know that the elements that are formed inbetween are not "Bi".

Expect me to ask more questions later on, as i will be starting to revise Leptons and all of that stuff that im really weak with. :D

5. Apr 5, 2014

### Curious3141

No, but mfb is right - in writing that way, it's wrong. It's OK to omit the symbol entirely (if you're just writing informally), but to actually put "Bi" there is wrong.

6. Apr 5, 2014

### LotusTK

The proton number?

7. Apr 5, 2014

### Curious3141

Steamking's post (that you're replying to) has vanished. But you're correct. I prefer to refer to it as the atomic number, because that's a good reminder that this is the number that determines what atom it is.