${ }_{26}^{55} \mathrm{Fe}$, which has an atomic mass of $54.938296 \mathrm{u}$ decays with a half-life of $2.7 \mathrm{y}$ to ${ }_{25}^{55} \mathrm{Mn}$, which has an atomic mass of $54.938047 \mathrm{u}$. Does this likely decay by a $\beta^{+}$process (B), or must it decay by electron capture $(\mathrm{E}) ?$
A) $\beta^{+}$process
B) must it decay by electron capture

Question

Quizplus · Accepted Answer

Electron capture is likely because the mass of the parent nucleus (${ }_{26}^{55} \mathrm{Fe}$) is greater than that of the daughter nucleus (${ }_{25}^{55} \mathrm{Mn}$), allowing for the decay process that does not emit a positron but instead captures an inner electron to convert a proton into a neutron.

2655Fe{ }_{26}^{55} \mathrm{Fe}2655​Fe , Which Has an Atomic Mass Of 54.938296u54.938296 \mathrm{u}54.938296u

${ }_{26}^{55} \mathrm{Fe}$ , Which Has an Atomic Mass Of $54.938296 \mathrm{u}$