Answer :
In alpha decay, an unstable nucleus emits an alpha particle, which consists of 2 protons and 2 neutrons. This results in the formation of a new element called the daughter nuclide.
Let's look at the alpha decay of radon-218:
Radon-218 has an atomic number of 86 (which means it has 86 protons) and a mass number of 218.
An alpha particle is represented by [tex]^4_2\text{He}[/tex], and subtracting it from radon-218 can be shown with the following equation:
[tex]^{218}_{86}\text{Rn} \rightarrow ^{4}_{2}\text{He} + ^{214}_{84}\text{X}[/tex]
Here:
The mass number of the daughter nuclide is calculated as: 218 - 4 = 214.
The atomic number of the daughter nuclide is: 86 - 2 = 84.
The element with atomic number 84 is polonium ([tex]\text{Po}[/tex]).
Thus, the daughter nuclide resulting from the alpha decay of radon-218 is polonium-214 ([tex]^{214}_{84}\text{Po}[/tex]).
This process not only transforms the element but also releases energy, contributing to radiation and is a significant process in both natural and artificial radioactive decay series.
