Explanation:
To check if a nuclear equation is balanced, we need to ensure that the sum of mass numbers (the top number) and the sum of atomic numbers (the bottom number) on the left side of the equation match their respective sum on the right side. In this case, the radon nucleus splits to form an astatine nucleus and a beta particle. A beta particle is essentially an electron, and its mass is considered negligible in nuclear reactions, thus, not taken into account.
Answer:
Given that there is no change in the mass number (219) and the atomic number changes by one unit (which is consistent with the emission of a Beta or an electron with charge -1), the reaction is balanced. Considering the options, the correct statement is: "mass of beta is zero, and it is an electron"
