Answer:
The answer to your question is: The mass number will be 4 units lower.
Explanation:
Alpha particles are Helium atoms, which have a mass number of 4 and atomic number of 2.
When an alpha particle is released, the original atom loses 2 protons and and 2 neutrons an we can see in the example.
²²⁶ ₈₈ Ra ⇒ ²²² ₈₆ Rn + ⁴₂ He
Protons are positively charged. When a nucleus emits an alpha particle, these changes happen: the mass number decreases by 4. the atomic number decreases by 2.
