# AAMC 5R Physical Sciences Question 33

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#### russianguy13

##### New Member
15+ Year Member
Was wondering if someone could please explain to me question #33.
Why is the answer an electron is being emitted and not a positron?
C-14 goes to N-14. Doesn't that mean that the Z number (atomic number) changed?

Well C-14 to N-14 means that a neutron turns into a proton. If a positron is emitted, a proton would turn into a neutron. If a positron is captured, a neutron would turn into a proton.

So since the question asks what is being emitted, it must be an electron, because a neutron turns into a proton, making the net amount of protons larger.

My school skipped nuclear physics/chemistry so I had to teach myself, and this is how I solve these:

We know we started with C-14, and we ended with N-14 and some particle. So I write out a chemical equation, like:

(14/6)C ---> (14/7)N + (?/?)?

Then it is clear to me that in order to balance the equation, the mystery particle has a mass of zero and a charge of -1. Yup, an electron (from the nucleus) got emitted.

There's usually only one question like this on the entire PS section, so I just take the time to write it out.

Was wondering if someone could please explain to me question #33.
Why is the answer an electron is being emitted and not a positron?
C-14 goes to N-14. Doesn't that mean that the Z number (atomic number) changed?