Chemistry Regents Practice Test

What happens when atoms of I-131 spontaneously decay?

1. They lose electrons.

2. They emit alpha particles.

3. They emit beta particles.

4. They gain protons.

The correct answer is: They emit beta particles.

Iodine-131 (I-131) undergoes a process known as beta decay. In this type of decay, a neutron in the nucleus of the I-131 atom is converted into a proton, resulting in the emission of a beta particle, which is essentially an electron. This transformation not only results in the loss of the neutron but also leads to an increase in the atomic number by one, changing the element from iodine (atomic number 53) to xenon (atomic number 54). This process is consistent with the behavior of many isotopes that have an imbalance in the neutron-to-proton ratio. The emission of beta particles allows the atom to move toward a more stable state by adjusting its nuclear composition. Therefore, the option stating that I-131 emits beta particles accurately describes what occurs during its spontaneous decay.