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A radioactive
nucleus that undergoes beta emission has a neutron in its nucleus convert
into a proton and an electron, then it ejects the electron. The remaining
nucleus has one more protons and one fewer neutron: the atomic number
increases by one and the mass number stays the same.
For example: Tritium, a radioactive isotope of hydrogen, undergoes beta
decay. Its product is an isotope of helium
- 31H -> 32He +
e-
Electrons are often denoted with the symbol
0-1e-: although an atomic number of -1 is a bit
odd, if you think in terms of adding up the products you'll get the reactant. In
the above reaction, adding an atomic number of 2 (He) and -1 (e-)
gives 1, the original atomic number.
Example: 146C is a radioactive isotope of carbon
that is used in dating organic materials. It is a beta emitter: what is the
product?
Solution: We keep the mass number the same (14) but increase the
atomic number by one (6+1 = 7) Atomic number 7 is nitrogen, so
- 146C -> 147N +
0-1e
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