Molecular Orbital Theory Flashcards
What is the significance of orbital hybridisation in chemistry?
Explains bonding characteristics and molecular structure
What is a Heteronuclear diatomic Molecular Orbital Energy Diagram used for?
To represent the energy levels of molecular orbitals in heteronuclear diatomic molecules
What is an example of resonance in biology?
The amide bond in proteins
What is the result of destructive interference of atomic wavefunctions?
Formation of antibonding orbitals
What types of bonds are defined in Molecular Orbital Theory?
- Sigma (σ) bonds
- Pi (π) bonds
How is a single bond characterized in terms of σ and π bonds?
A single bond is a σ-bond
What characterizes a double bond in terms of σ and π bonds?
A double bond is a σ-bond plus one π-bond
What characterizes a triple bond in terms of σ and π bonds?
A triple bond is a σ-bond plus two π-bonds
What is the relationship between the s character of a hybrid orbital and bond length?
As s character increases, bond length decreases
What is the order of decreasing s character in hybrid orbitals?
sp > sp2 > sp3
Define paramagnetism.
A substance can be drawn into a magnetic field due to unpaired electron spins
Define diamagnetism.
Molecules without unpaired electron spins are diamagnetic
Fill in the blank: A double bond consists of a σ-bond plus _______.
one π-bond
True or False: A single bond can be formed by two π-bonds.
False
What diagram is used to show the arrangement of valence electrons in O2 2-?
Molecular orbital (MO) diagram
What does the term ‘bond order’ refer to?
The difference between the number of bonding and antibonding electrons divided by two
What is the role of Hund’s rule in filling atomic orbitals?
Electrons fill degenerate orbitals singly before pairing up
How does the energy of bonding orbitals compare to atomic orbitals?
Bonding orbitals have lower energy than atomic orbitals
What are the two types of overlap that can occur to form σ bonds?
- s-s overlap
- s-p overlap
- p-p overlap
What is the effect of multiple bonding?
Bond length depends strongly on bond order
sp3-sp3 —> C-C = 1.54
sp3-sp3 —> C-O = 1.42
sp2-sp2 —> C=C = 1.34
sp2-sp2 —> C=O = 1.22
sp-sp —> C-C (triple bond) = 1.20
What is the effect of hybridisation on the length of single bonds?
C-H and C-C bonds shorten slightly with increased ‘s’ character on carbon
Sp3-sp3 —> C-C = 1.54
Sp3 —> C-H = 1.09
Sp3-sp2 —> C-C = 1.50
Sp2 —> C-H = 1.086
Sp3-sp —> C-C = 1.47
Sp —> C-H = 1.06
What are the key molecules we need to know?
