Molecular orbitals homonuclear diatomic molecules
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What are homonuclear diatomic molecules?
Molecules that consist of two atoms from the same element
What are the 5 steps involved?
• Construct molecular orbitals • For each combination of two atomic orbitals, obtain two molecular orbitals • Allocate valence electrons to the molecular orbitals • Calculate bond order • Look for unpaired electrons
What do two 2s orbitals combine to form?
they combine in phase and out of phase to give σ and σ* MO
What do two 2Pz orbitals combine to form?
They combine in phase and out of phase to give σ and σ* MO
What do two 2Px and 2Py orbitals combine to form?
They combine in phase and out of phase to give two π and two π* MO
What effect does a large overlap integral have on bonding MO’s?
The will be more stable and have less energy
What effect does a large overlap integral have on antibonding MO’s?
They will be less stable and have more energy
Which is higher in energy, 2p or 2s?
2p
What other symbols can be given to the symmetry of the atoms towards the mathematical operation of inversion?
g u
What does g mean? (MO symmetry)
Gerade Even
What does u mean? (MO symmetry)
Ungerade Uneven
When allocating valence electrons, which orbitals are filled first and why?
Bonding Lower in energy
Which electrons do you ignore when allocating electrons to molecular energy diagrams?
Core electrons eg. 1s2
How do you calculate bond order?
1/2 (Number of bonding electrons - number of antibondung electrons)
What does a higher bond order mean for the type of bond?
Shorter and stronger
What does paramagnetic mean?
A substance that has unpaired electrons
What does diamagnetic mean?
A substance that has no unpaired electrons
When can s and p mix?
When they have the same geometry
How do you name the orbitals when there is sp mixing?
eg. σ1, σ2 etc
What are the consequences of adding more antibonding electrons?
bond strength decreases bond length increases