Chemistry also deals with transformations of matter including changes that occur when cues react are ex cited(electronically, vibrationally, or rotationally ) or undergo geometrical rearrangements. Again, theory forms the cornerstone that allows experimental probes of chemical change to be connected to the molecular level and that allows simulations of such changes Molecular excitation may or may not involve altering the electronic structure of the molecule. vibrational and rotational excitation do not but electronic excitation ionization, and electron attachment do. as illustrated in Fig. 5. 3 where a bi-molecular reaction is displayed, chemical reactions involve breaking some bonds and forming others and thus involve rearrangement of the electrons among various molecular orbitals Figure 5.3 Two bimolecular reactions a and b show an atom combining with a diatomic c and d show an atom abstracting an atom from a diatomic9 Chemistry also deals with transformations of matter including changes that occur when molecules react, are excited (electronically, vibrationally, or rotationally), or undergo geometrical rearrangements. Again, theory forms the cornerstone that allows experimental probes of chemical change to be connected to the molecular level and that allows simulations of such changes. Molecular excitation may or may not involve altering the electronic structure of the molecule; vibrational and rotational excitation do not, but electronic excitation, ionization, and electron attachment do. As illustrated in Fig. 5.3 where a bi-molecular reaction is displayed, chemical reactions involve breaking some bonds and forming others, and thus involve rearrangement of the electrons among various molecular orbitals. Figure 5.3 Two bimolecular reactions; a and b show an atom combining with a diatomic; c and d show an atom abstracting an atom from a diatomic