Question

During an $\alpha$-decay, the atomic number of parent element _____________ and mass number ___________ by $4$.

Answer 1

During an $\alpha$ - decay, the atomic number of the parent element is decreased by 2 and mass number is decreased by 4.

When an alpha particle is emitted from a nucleus loses two protons and two neutrons. The new element is formed that is two planes lower in the periodic table than the original element.