Answer: The correct answer is decreased by two.
Explanation:
Alpha particle is emitted when a radioactive isotope undergoes alpha decay process. In this process a heavier particle decays into a lighter particle with the release of alpha particle. The alpha particle carries a mass of 4 units and a charge of +2 units.
The atomic number of the atom gets reduced by 2 units and atomic mass of the same atom gets reduced by 4 units.
The equation representing alpha decay process is:
[tex]_Z^A\textrm{X}\rightarrow _{Z-2}^{A-4}\textrm{Y}+_2^4\alpha[/tex]
Hence, the correct answer is decreased by two.
