Question

The OH radical (i.e., OH -) has been observed in interstellar space.

a.) Formulate a description of the electronic structure of OH using molecular orbital theory (Note: The VOIE of hydrogen is 13.6 eV).

b.) Sketch what you would expect to observe for the photoelectron spectrum of OH.

c.) Is the orbital that houses the radical in OH primarily oxygen in character or hydrogen in character? Explain.

d.) The first ionization energy of OH is 13.2 eV and that of HF is 16.05 eV. The difference between these values is almost identical to the difference between the valence orbital ionization energies of the 2p orbitals of the oxygen and fluorine. Use your understanding of the molecular orbital diagrams of these two molecules to suggest a reason for this fact.

Answer 1

OH has 9 electrons(8 electrons from an oxygen atom and 1 electron from H atom).molecular orbital theory(MO) is a linear combination of atomic orbitals(LCAO) and these atomic orbitals are described by wavefunctions if the electron clouds on these atoms approach and overlap and form a MO (psi MO).

a) b) the photoelectron spectrum support the existence of Molecular Orbitals.The energy required to eject an electron is ionization energy. The ionization energy of an electron depends on MO the electron occupies, the lower the energy of an ionization energy higher the MO energy. c) it's primarily O atom, as it doesn't pair it's in the nonbonding electrons, so a radical formation is due to those nonbonding electrons in O atom.

d) The OH molecule and HF molecule, highest energy MO is nonbonding electrons formed by 2px,2py in both cases so that,s why its equivalent to valence orbital ionization energy of 2p orbitals of oxygen and fluorine.