Information The center of mass of a diatomic molecule is defined as shown in Figure 1 . Figure 1. Definition of the Center of Mass of a Diatomic Molecule. m1r1=m2r2 Model 2: Translational Energy. direction of motion of center of mass Translational Motion: Center of mass of molecule moves in some direction. center of mass for CO molecule The translational eneray of a molecule can be thought of as 21mv2, where alf of the mass of the molecule, m, is located at the center of mass of the molecule. Critical Thinking Questions 4. Is the center of mass of a diatomic molecule closer to the heavier atom or the lighter. of the molecule, m, is located at the center of mass of the molecule. tical Thinking Questions Is the center of mass of a diatomic molecule closer to the heavier atom or the lighter atom? 4 ChemActivity 1 The Energies of Molecules 5. Which atom is the carbon atom in Model 2? Explain your answer. 6. The intemuclear distance (bond length) in CO is 113pm. The triple-bond radius of a carbon atom is 60pm, and the triple-bond radius of an oxygen atom is 53pm. Does this mean that the center of mass of CO is located on the straight line connecting the two nuclei and 60pm from the carbon nucleus? Exercises 1. The molecular mass of 12C is exactly 12g/ mole. The molecular mass of 16O is 15.995g/mole. Determine the mass of one carbon-12 atom (to four significant figures). Determine the mass of one oxygen- 16 atom (to four significant figures). 2. Determine the location of the center of mass of 12C16O to four significant figures given that the internuclear distance is 113.1pm