What happens to the atomic number and mass number in alpha decay?

What happens to the atomic number and mass number in alpha decay?

• A. Atomic number decreases by 2; mass number decreases by 4; an alpha particle is emitted.
• B. Atomic number increases by 2; mass increases by 4; alpha particle emitted.
• C. Atomic number decreases by 4; mass decreases by 2; an alpha particle is emitted.
• D. Atomic number increases by 1; mass unchanged; gamma emitted.

Answer: (A)