Question

1. For the homonuclear diatomic molecules across the periodic table from H2 to Nez (10 molecules in all), make a MO diagram like the figure, and fill in the electrons. Be sure to get the order of the orbitals correct (see Fig. 11.14 of textbook). For each molecule, give the bond order and whether or not it's paramagnetic (unpaired spins). I know this seems like a pretty basic question, but it's important for chemists to have this model embedded in memory. Пар 29 | | |

Answer 1

WeWe can build up MO diagram for homonuclear diatomics from our combination of AOs. It is important to realize that the actually MO calculation will yield specific energies and bond lengths that are unique for each diatomic. While this is true, the general ordering of the MOs and their relative energies compared to the AOs is consistant for the 2nd row homonuclear diatomics. Thus if we know this diagram, we can answer a variety of questions regarding these molecules by simply placing the appropriate number of electrons into the diagram.

The following two diagrams are the MO diagrams for the 2nd row diatomic molecules. There are two diagrams because the order of the energy levels is slightly different for O2 and F2 than for the rest of the diatomic molecules. Note the changing in the order of the σ and π bonding orbitals from the 2p atomic orbitals.

Please see image for electronic configuration and MO diagram.

Among all these 10 molecules only B2,O2 ,F2 are paramagnetic because of presence of unpaired electrons.

Bond order:

H2= 1

He2= 0

Li2= 1

Be2= 0

B2= 1

C2= 2

N2= 3

O2= 2

F2= 1

Ne2=1.