Mass/charge balance of Beta decay/nuclear reactions

[cashmoney805]

Homework Statement

There are three different reactions we did in class.
B-: ₆C¹⁴ --> ₇N¹⁴ + e-
B+: ₆C¹¹ --> ₅B₁₁ + e+
Nuclear rxn: alpha particle + ₇N¹⁴ --> ₈O¹⁷ + e+

Homework Equations

Q tot = (mass inital - mass final) * 931.5 MeV
Charge balance

The Attempt at a Solution

In class, for B- the teacher wrote down:
Q= (Mass of C nucleus) - (mass of N nucleus) - 1 e-
= (mass of C atom - 6 e-) - (mass of N atom - 7 e-) - (mass of 1 e-)
so -6 -(-7) - 1 = 0 so Q= (mass of C atom) - (mass of N atom)

B+
Q = (mass of C nuc) - (Mass of B nuc) - (mass of e+)
Q= (mass of C atom - 6 e-) - (mass of B atom - 5 e-) - mass of 1 e-
Q= -6 -(-5) -1 = -2, so he said Q total = (mass of C) - (mass of B + 2e-)

Nuclear rxn
Q = (mass of alpha nuc) + (mass of N nuc) - (mass of O nuc) - (mass of e+)
Q = (mass of He - 2 e-) + (mass of N atom - 7 e-) - (mass of O atom - 8 e-) - (mass of e+)
Q = -2 + -7 - (-8) -1 = -2 e-
However, he said in class that the Q = (mass of alpha particle + mass of N atom) - (mass of O atom)
Can someone please clear this up for me? I really don't get the charge/mass balance. Thanks so much

 

[RoryP]

so basically you have to make sure that the mass and charge is the same before the reaction as it is after.
remember energy can't be created, it simply changes from one form to another =]
and also for B- emission you would have an anti-electron-neutrino and for B+ emission you would have an electron-neutrino!