Chapter 3 - Bonding

Question 1

Which is more stable: a bonding orbital or an anti-bonding orbital? Which has higher energy?

Answer 1

More Stable: Bonding orbitals

Higher Energy: Anti-bonding orbitals

Question 2

What differences would be observed in a molecule containing a double bond compared to the same molecule containing a single bond?

Answer 2

The differences would be in bond length (shorter in double bond), bond energy (higher in double bond), and molecular rigidity (higher in double bond).

Question 3

Rank the 4 orbital types in decreasing order of strength.

Answer 3

1. Triple Bond
2. Double Bond
3. Sigma Bond (Single)
4. Pi Bond (Multiple)

Question 4

What are the s- and p- characters of sp?

Answer 4

50% s character; 50% p character

Question 5

What are the s- and p- characters of sp2?

Answer 5

33% s character; 67% p character

Question 6

What are the s- and p- characters of sp3?

Answer 6

25% s character; 75% p character

Question 7

What is Resonance?

Answer 7

Describes the delocalization of electrons in molecules that have conjugated bonds. Resonance increases the stability of a molecule.

Question 8

When does Conjugation occur?

Answer 8

When single and multiple bonds alternate, creating a system of unhybridized p-orbitals down the backbone of the molecule through which pi electrons can delocalize.

Question 9

How does the true electron density of a compound relate to its Resonance Structure?

Answer 9

The true electron density is a weighted average of the resonance structures of a given compound, favouring the most stable structures.

Question 10

When do Molecular Orbitals form?

Answer 10

When two atomic orbitals combine.

Question 11

What is Hybridization?

Answer 11

A way of making all bones to the centre atom equivalent to each other.

Question 12

When do Hybrid Orbitals form?

Answer 12

Hybrid Orbitals are formed by mixing different types of orbitals. use math to mix the following orbitals:

• sp3
• sp2
• sp

Question 13

What characteristics mark an sp3 orbital?

Answer 13

1 atom with all single bonds (sigma bonds).

Tetrahedral geometry with 109.5 degree bond angles and have no unhybridized p-orbitals to form pi bonds.

Question 14

What characteristics mark an sp2 orbital?

Answer 14

1 double bond (1 sigma and 1 pi bond).

Seen in alkenes. They form trigonal planar geometry with 120 degree bond angles. Third orbital of each carbon is left unhybridized.

Question 15

What characteristics mark an sp orbital?

Answer 15

Triple bond (1 sigma and 2 pi bonds)

To form a triple bond (alkynes). They have a linear structure.

Question 16

How are Pi Bonds formed?

Answer 16

Formed by the parallel overlap of unhybridized p-orbitals.

Question 17

How are Bonding Orbitals formed?

Answer 17

Created by head-to-head or tail-to-tail overlap of atomic orbitals of the same sign and are energetically favourable.

Question 18

How are Anti-Bonding Orbitals formed?

Answer 18

Created by head-to-head or tail-to-tail overlap of atomic orbitals that have opposite signs and are energetically unfavourable.