Rn) decays by alpha decay to an isotope of polonium (Po) with a mass number of

Radon (Rn) undergoes alpha decay by emitting an alpha particle, which consists of 2 protons and 2 neutrons. This means that both the atomic number and the mass number of radon will decrease.

1. Identify the atomic number and mass number of Radon. Radon (Rn) has an atomic number of 86 and a mass number of 222.

2. Understand alpha decay. In alpha decay, an atom emits an alpha particle. An alpha particle has 2 protons and 2 neutrons.

3. Calculate the atomic number and mass number of the resulting atom after alpha decay. After emitting an alpha particle, the atomic number of radon will decrease by 2 and the mass number will decrease by 4.

So, the atomic number of the resulting polonium (Po) isotope will be 84 (86-2) and the mass number will be 218 (222-4).

Therefore, Radon (Rn) decays by alpha decay to an isotope of polonium (Po) with a mass number of 218.