Describe what happens to a carbon-11 atom when it undergoes positron emission.

C11 ^boron+positron

Explanation:the above reaction is nuclear reaction.

Positron emission causes the decrease in atomic number by one.

As in above example carbon-11is converted into boron isotop which has atomic number of 5.

Note that the energy emitted depends on the isotope that is decaying; the figure of 0.96 MeV applies only to the decay of carbon-11. The short-lived positron emitting isotopes 11C, 13N, 15O and 18F used for positron emission tomography are typically produced by proton irradiation of natural or enriched targets.

Explanation: They won't last long since the isotope is decaying.