There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br2 molecules, and the mass of a Br2 molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br2 consists of three peaks. Mass (amu) Relative Size 157.836 0.2569 159.834 0.4999 161.832 0.2432 (a) What is the origin of each peak (of what isotopes does each consist)? (Enter all particles in the form AX.) mass 157.836 amu 159.834 amu 161.832 amu molecule (b) What is the mass of each isotope? (Calculate using the given masses.) lighter isotope amu heavier isotope amu (c) Determine the average molecular mass of a Br2 molecule. amu (d) Determine the average atomic mass of a bromine atom. amu (e) Calculate the abundances of the two isotopes.