Valence Bond Theory, Hybridization, and Molecular Geometry Flashcards
What is the valence bond theory?
The theory that covalent bond forms when two atoms approach each other closely so that an orbital containing 1 electron overlaps with another orbital containing 1 electron. The electrons are attracted to the nuclei of both pairs, thus bonding the atoms together.
What is a sigma bond
Bonds that are formed by the head on overlapping of two atomic orbitals. Sigma bonds are always single bond.
What happens to energy during bond breaking/bonding?
Energy is released during bond making. Energy is absorbed during bond breaking.
Why is energy absorbed during bond breaking?
Energy must be applied in order to break bonds. Bonds cannot be broken spontaneously.
Analogy: You need to burn the wood with fire (adding energy) or else the wood will never burn.
What is Bond Length? What does bond length imply about the hybrid orbitals?
The optimal distance between nuclei that leads to maximum stability.
If the orbitals of the bonded atoms are too close, they repel each other (electron to electron). If the orbitals of the bonded atoms are too far, the bonding is weak.
Bond length imply that the hybrid orbitals orient themselves to maximize distance between orbitals to minimize electron to electron repulsion.
Hybridization
Mixing two atomic orbitals to give rise to a new type of hybridized orbitals.
What happens when an s orbital combines with three p orbitals? When does this usually happen?
The result is 4 sp3 orbital.
This usually happen when there is a single bond.
The superscript 3 tells how many of each type of atomic orbital combined to form the hybrid. In this case, there were 3 p orbitals used to make the hybrid.
What happens when you combine 4 sp3 orbitals?
The four sp3 orbitals orient into a tetrahedral molecular geometry.
Why is an sp3 orbital unsymmetrical about the nucleus?
The two lobes of the p orbital have different algebraic signs. The positive p lobe adds to the s orbital but the negative p lobe subtracts from the s orbital.
What happens when an s orbital combines with two of the three p orbitals? When does this usually happen?
Three sp2 hybrid orbitals result and one 2p orbital remained unchanged.
This usually happen when there is a double bond.
What is a pi bond?
Bonds that are formed by the sideway overlapping of two atomic orbitals
What happens when you combine 3 sp2 orbitals?
The sp2 orbitals orient into a trigonal planar molecular geometry
What happens when an s orbital combines with only one out of the three p orbitals? When does this usually happen?
Two sp orbitals result with 2 unchanged p orbitals. This usually happens during a triple bond.
What happens when you combine two sp orbitals?
The two sp orbitals orient into a linear molecular geometry.
