Question

An atom of radon gas emits an alpha particle as shown below. Radon-222 has 86 protons and 136 neutrons. What daughter product will form from this decay?

Answer 1

Correct Answer: B. Polonium-218 (84 protons)

Explanation: The original atomic number of radon is 86, and the mass number is 222 (136 neutrons plus 86 protons). The emission of an alpha particle will reduce the mass number by 4 and the atomic number by 2. Therefore, radon-222 (86 protons) yields polonium-218 (84 protons).

Answer 2

The answer is Polonium-218 (84 protons).

Alpha particles consist of two protons and two neutrons. So, mass is 4 (2+2) amu .
When an atom of emits an alpha particle, its atomic number will be reduced by 2 and a mass number will be reduced by 4:
→ + .

After emission of the alpha particle from Radon-222 with 86 protons, the daughter product will have the atomic number reduced by 2: 86-2 = 84 and the mass number reduced by 4: 222-4=218:
→ + .