Book: Ch. 11

Question 1

Define: valence bond (VB) theory

Answer 1

Basic principle says a covalent bond forms when orbitals of two atoms overlap and a pair of electrons occupy the overlap region.

Question 2

Define: hybridization

Answer 2

The process of orbital mixing

Question 3

Define: hybrid orbitals

Answer 3

Atomic orbitals resulting from hybridization.

Question 4

Define: sp hybrid orbitals

Answer 4

One s and one p mix to form two equivalent sp hybrid orbitals that are orientated 180º apart.

Question 5

Define: sp² hybrid orbitals

Answer 5

Mixing one s and two p orbitals gives three sp² hybrid orbitals. This results in the trigonal planar electron-group arrangement, which gives rise to bent and trigonal planar molecular shape.

Question 6

Define: sp³ hybrid orbitals

Answer 6

Result from mixing one s and three p orbitals. Gives rise to the tetrahedral arrangement.

Question 7

Define: sp³d hybrid orbitals

Answer 7

Mix of one 3s, three 3p, and one of the five 3d orbitals gives five sp³d hybrid orbitals. These point to the corners of a trigonal bipyramid.

Question 8

Define: sp³d² hybrid orbitals

Answer 8

Mixing one 3s, three 3p, and two 3d orbitals gives six sp³d² hybrid orbitals, which point to the corners of an octahedron.

Question 9

Define: sigma (σ) bond

Answer 9

Formed by the end-to-end overlap of orbitals, a sigma bond has its highest electron density along the bond axis and is shaped like an ellipse rotated about its long axis. All single bonds are σ bonds.

Question 10

Define: pi (π) bond

Answer 10

Formed by side to side overlap of orbitals, a pi bond has two regions (lobes) of electron density, one above and one below the σ-bond axis. The two electrons in one π bond occupy both lobes. A double bond consists of one σ bond and one π bond.

Question 11

Define: molecular orbital (MO) theory

Answer 11

Treatment of molecules that posits that just as an atom has atomic orbitals of given energies and shapes that are occupied by the atom’s electrons, a molecule has molecular orbitals (MOs) of given energies and shapes occupied by the molecule’s electrons.

Question 12

Define: molecular orbitals (MOs)

Answer 12

Orbitals of given energies and shapes occupied by the electrons of a molecule.

Question 13

Define: bonding MO

Answer 13

Combination of wave functions of overlapping atomic orbitals gives bonding MOs, which have a region of high electron density between the nuclei.

Question 14

Define: anti-bonding MO

Answer 14

When wave functions subtract from each other, anti-bonding MOs form, which have nodes, regions of zero electron density between the nuclei.

Question 15

Define: sigma (σ) MOs

Answer 15

Cylindrically symmetric bonds about an imaginary line between the nuclei—the bonding and antibonding MOs of H₂ are an example.

Question 16

Define: molecular orbital (MO) diagram

Answer 16

Shows the relative energy and number of electrons for each MO, as well as for the AOs from which they are formed.

Question 17

Define: MO bond order

Answer 17

Bond order = 1/2 no. of e- in bonding MOs - 1/2 no. of e- in antibonding MOs

Question 18

Define: homonuclear diatomic molecules

Answer 18

Comprised of two identical atoms.

Question 19

Define: pi (π) MOs

Answer 19

Side-to-side combination of p orbitals gives a pair of π MOs, π_2p and π_2p*.

Question 20

Define: nonbonding MOs

Answer 20

MOs not involved in bonding. These have the same energy as the isolated AOs.