Massspectrometry is more often applied to molecules than to atoms. We will see in Chapter 3 that the molecular weight of a molecule is the sum of the atomic weights of the atoms in the molecule. The mass spectrum of H₂ is taken under conditions that prevent decomposition into H atoms. The two naturally occurring isotopes of hydrogen are ¹H (atomic mass = 1.00783 amu; abundance 99.9885%) and ²H (atomic mass = 2.01410; abundance 0.0115%). (c) Which peak will be the largest, and which the smallest?