Valence Bond Theory

Question 1

What is a sigma bond?

Answer 1

The electron density concentrates along the internuclear axis. Hybridized orbitals, overlap in one space.

Question 2

What is a pi bond?

Answer 2

Covalent bond that results in side by side overlap of p orbitals. The regions of overlap lie on opposite sides of the internuclear axis. Unhybridized orbitals, overlap in two spaces.

Question 3

What is always the first bond that will be formed?

Answer 3

A sigma bond

Question 4

In general, what is valence bond theory?

Answer 4

The consequence of overlap between atomic orbitals that creates a region where one pair of electrons is shared between two atoms

Question 5

How far are sp orbitals from each other?

Answer 5

180 degrees

Question 6

What are the characteristics of sp2 orbitals?

Answer 6

• 3 sp2 hybridized, 1 unhybridized p orbital
• Trigonal planar
• Any atom surrounded by 3 regions of electron density (including lone pairs on the central atom and double bonds)

Question 7

What are the sp3 orbitals?

Answer 7

• 4 sp3 hybridized, 0 unhybridized p orbitlas
• Tetrahedral
• Any atom surrounded by 4 regions of electron density (including lone pairs)

Question 8

What is constructive overlap?

Answer 8

Phase of orbitals is the same so a bond forms

Question 9

What is destructive overlap?

Answer 9

Phase of orbitals is different so an antibond will form

Question 10

What are the energies of bonding and antibonding orbitals?

Answer 10

• Bonding orbitals are lower energy (more stable)
• Antibonding orbitals are higher energy (more unstable)

Question 11

What type of orbitals overlap?

Answer 11

• Orbitals of similar energy
• Orbitals of similar symmetry
• Bonding and antibonding (always empty in VBT) overlaps occur