Homonuclear Diatomics Flashcards
What is equation for the linear combination of atomic orbitals?
MO = (c1 x AO1) + (c2 x AO2)
where c1 and c2 are coefficients used to take into account the symmetry of the molecule.
What assumptions are made in the linear combination of atomic orbitals?
That the nuclei are a fixed distance apart.
What are the two ways in which sine waves (and atomic orbitals) can be combined?
Constructively (in-phase) or destructively (out-of-phase).
Why is a bonding MO lowered in energy?
The greatest electron density is in the internuclear space, so nuclei are attracted closer together. As there is no node the electrons are more delocalised and the electrons therefore have lower kinetic energy.
Why is an anti-bonding MO raised in energy?
Most electron density is outside of the internuclear space, exerting a force that pulls the electrons apart. There is also a node that constrains the movement of electrons, so they have more kinetic energy.
When combining n atomic orbitals, how many molecular orbitals are produced?
n
When do the bonding and anti-bonding MOs have their minimum energy?
For bonding MOs the minimum energy is at equilibrium bond length. For anti-bonding MOs, the minimum energy is when the atoms are at infinite separation.
When is a π MO formed?
Side-on overlap of p orbitals.
What is the letter given to a symmetrical MO?
‘g’ for gerade.
What is the letter given to an asymmetrical MO?
‘u’ for ungerade.
What might be used to denote an anti-bonding MO?
An asterisk
What factors determine how well AOs combine?
Symmetry, energy difference and the size of the orbitals.
In O2 and F2, is sp mixing significant?
No.
In diatomics of less electronegative elements (N2 and below), is sp mixing significant?
Yes.
When sp mixing takes place what is the energy of the π bonding MO relative to the σ bonding MO?
The π bonding MO is lower in energy.
