Question

during nuclear decay, a new isotope is created. how is the nucleus of the new isotope different from the parent if the parent isotope has undergone alpha decay?
a the atomic number decreases by 2 and the mass decreases by 4.
b the atomic number decreases by 2 and the mass increases by 1.
c the atomic number increases by 2 and the mass remains the same.
d the atomic number remains the same and the mass decreases by 1.

Explanation:

Alpha decay involves the emission of an alpha particle ($\ce{^4_2He}$). An alpha particle has 2 protons (so atomic number decreases by 2) and 4 nucleons (2 protons + 2 neutrons, so mass number decreases by 4).

Answer:

A. The atomic number decreases by 2 and the mass decreases by 4.