[poll id=”26″]
ANSWER : A
Begin by looking at the reactant side and noting down the number of mass number and protons (235 and 92 respectively). These numbers have to match the total numbers on the product side. The 2 alpha-decay and 1 beta-decay give you a mass of 8, which means it is 227 short of the mass number in the reactants. They also produce a (2+2-1=3) number of protons, 89 short of balancing the reactant number of protons. Thus, your missing daughter nuclei will have a mass of 227 and 89 protons. Looking at a periodic table (which will be provided in the OAT exam), the atom Ac has 89 protons.