Molecular Orbital Diagrams Worksheet printable pdf download

Morning class week 5 day 1: Diatomic molecular

orbital diagrams without sp hybridization

1. Making MO diagrams

Making more traditional outside-to inside MO diagrams requires knowing two diﬀerent

things: the ﬂow diagram by which MO diagrams are generated and the rules by which

the ﬂow-chart is processed.

(a) The ﬂow chart: There are four steps.

i. Place the two atomic orbital (AO) energy diagrams on the two sides of the

sheet of paper.

ii. Based on the atomic electron conﬁguration, place the correct electron ﬁllings

for the two AO energy diagrams, one on each side.

iii. Mix pairs of AOs to derive two MOs. One of the MOs is more bonding, the

other more antibonding. They are indicated by horizontal lines in the center

of the page. MO balloon drawings are placed next to each of these central

horizontal lines.

iv. Follow the Aufbau principle and ﬁll the central horizontal lines with the

correct number of electrons.

(b) The rules: There are three rules for the making of MO diagrams.

i. In a minimal basis set MO diagram, the number of MOs equals the number

of AOs.

ii. When two orbitals combine, they combine to make two new orbitals. The

original orbitals combine to make the lowest and highest energy combinations

possible.

iii. Orbitals which are initially close in energy interact stronger than orbitals

which are initially far apart in energy. When two orbitals of diﬀerent energy

combine, the resultant low energy combination resembles more the initially

lower energy orbital; the resultant high energy combination resembles more

the initially high energy orbital. Two orbitals of equal initial energy combine

to make two new orbitals with equal contributions from the two starting

orbitals equally.

MO diagram you previously drew and detemine where the three

rules were applied in the making of the diagram.

2. We apply the above ideas to make MO diagrams for a variety of diﬀerent

diatomic molecules.

(a) Draw an MO diagram for Be

using only the 1s and 2s Be AOs.

(b) Draw an MO diagram for Be

using only the 2s Be AOs.

Molecular Orbital Diagrams Worksheet