Chemistry - A Molecular Science

Chapter 6 Molecular Structure & Bonding

orbitals must first be mixed in a process calle

d hybridization. The r

esulting hybrid orbitals

are used to form the

bonds and hold the lone pairs. The hyσ

bridization of an atom is used

to describe both the bonding and structure around the atom because hybrid orbitals have the geometries required by VSEPR. The orbitals

that are not used to construct the hybrid

orbitals are used to form

bonds. π

In molecular orbital theory, electrons occupy

molecular orbitals just as the electrons in

an atom occupy atomic orbitals. The molecula

r orbitals are constructed by combining the

atomic orbitals of different atoms. Unli

ke the bonds produced in valence bond theory,

molecular orbitals can be delocalized over several atoms, which explains the observations that valence bond theory invokes resonance to explain.

After studying the material presented in this chapter, you should be able to: 1. predict molecular and ionic shapes based on VSEPR theory (Section 6.1); 2. determine whether an atom obeys the octet ru

le or uses an expanded octet (Section 6.2);

3. predict the shapes of molecules and ions wi

th atoms using expanded octets (Section 6.2);

4. visualize the three-dimensional arrangem

ent of atoms around a central atom in a

complicated molecule (Section 6.3);

5. represent the overlap of tw

o atomic orbitals qualitatively with a drawing (Section 6.4);

6. define and identify

andσ

π

bonds (Sections 6.4 and 6.5);

7. draw the

and σ

components of a multiple bond (Section 6.4); π

8. determine an atom’s hybridization, draw pictures of hybrid orbitals, and account for

molecular shapes based on hybridization (Section 6.4);

9. construct molecular orbitals of simple syst

ems and explain resonance in terms of molecular

orbitals (Section 6.5);

10.

determine whether an MO is bonding, antibonding, or nonbonding (Section 6.5); and

11.

identify the HOMO and LUMO for a molecule given its MO diagram and the number of electrons that go in it (Section 6.5).

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