${ }_{35}^{79} \mathrm{Br}$ has an atomic mass of $78.918336 \mathrm{u}$, and ${ }_{.36}^{79} \mathrm{Kr}$ has an atomic mass of $78.920084 \mathrm{u}$. Which is the correct decay process (or the likeliest if more than one is possible)?
A) ${ }^{79} \mathrm{Kr} \rightarrow{ }^{79} \mathrm{Br}+v$
B) ${ }^{79} \mathrm{Kr} \rightarrow{ }^{79} \mathrm{Br}+\mathbf{e}^{-}+\bar{v}$
C) ${ }^{79} \mathrm{Kr} \rightarrow{ }^{79} \mathrm{Br}+e^{+}+v$
D) ${ }^{79} \mathrm{Br} \rightarrow{ }^{79} \mathrm{Kr}+e^{-}+\bar{v}$
E) ${ }^{79} \mathrm{Br} \rightarrow{ }^{79} \mathrm{Kr}+e^{+}+v$

Question

Quizplus · Accepted Answer

${ }^{79} \mathrm{Kr}$ decaying into ${ }^{79} \mathrm{Br}$ with the emission of an electron ($e^{-}$) and an antineutrino ($\bar{v}$) is an example of beta-minus ($\beta^{-}$) decay, which occurs when a neutron in the nucleus of an atom decays into a proton, an electron, and an antineutrino. This process increases the atomic number by 1 while keeping the atomic mass number the same, consistent with the transition from krypton ($Z=36$) to bromine ($Z=35$).

3579Br{ }_{35}^{79} \mathrm{Br}3579​Br Has an Atomic Mass Of 78.918336u78.918336 \mathrm{u}78.918336u , And

${ }_{35}^{79} \mathrm{Br}$ Has an Atomic Mass Of $78.918336 \mathrm{u}$ , And