For a negative beta particle why is it that its mass number is 0 and its atomic number is -1 because if : mass number = num of (protons + neutrons) and atomic number= num of (protons) , why wouldn't the mass number be -1 aswell , I know the mass of an electron is 0 but if protons make up the mass and atomic numbers then why is just the atomic number -1?
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The beta particle is an electron. – probably_someone Apr 18 '18 at 19:07
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Yeah but what makes it's atomic number -1 , i'm sure it's the charge but why is the atomic number now charge ? – Fred Apr 18 '18 at 19:09
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2The atomic number was always charge. – probably_someone Apr 18 '18 at 19:09
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I thought it was the total number of protons? – Fred Apr 18 '18 at 19:10
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thats what I don't get why is it 0 over -1 ? – Fred Apr 18 '18 at 19:11
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The mass number is zero because the electron has negligible mass. The atomic number is -1 because the electron has a charge of $-e$. – probably_someone Apr 18 '18 at 19:11
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where did you find these definitions? the mass number is the same as the baryon number and J.G. 's answer s fine. Who needs to give an atomic number to the electron? Definition of atomic number is the number of protons, there are no protons in the electron the muon the neutrino ... . -1 atomic answer is nonsense whoever wrote it, or you are reading it wrong in a table – anna v Apr 18 '18 at 19:51
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When a nucleon emits a $\beta^-$, which you could think of as subtracting a $\beta^-$ from the nucleus, the mass of the nucleus stays practically the same, and the atomic number goes up by one. – Solomon Slow Apr 18 '18 at 21:16
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The so-called mass number is really a nucleon count, since the neutron's mass is very slightly more than the proton's, while the electron's is nearly 2000 times smaller. In fact, we can think of it more fundamentally as a conserved quantity called the baryon number (for which each nucleon scores 1, while the electron scores 0).
J.G.
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1A related answer expands on baryon number as a conserved quantity, but also discusses some issues that are probably not yet useful to this asker. – rob Apr 18 '18 at 20:13
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In reality during a nuclear reaction, Mass number and electric charge is conserved rather than atomic number which you are emphasising. So your problem will get sorted. Here electric charge means total charge on the constituent of nuclear reaction.
