Linear combination of atomic orbitals
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What happens when you bring 2 nuclei together?
the 1s orbitals begin to overlap The electron density is spread between the first nucleus, the second nucleus and the region in between
What are the effects of the enhanced electron density?
Shields the positively charged nuclei from each other The electron is strongly attracted by both nuclei at the same time
What happens if the electron is near the left nucleus?
The influence of one of the nucleus is greater than the other The behaviour of the electron would be very similar to that in a 1s atomic orbital of the nucleus
What happens if the electron is near the right hand nucleus?
Influence of the other nucleus is greater The behaviour of the electron would be very similar to that in a 1s atomic orbital of the nucleus
What happens if the electron is between the two nucleus?
It feels the influence of both nuclei
What is linear combination of atomic orbitals?
The wavefunction describing the molecular orbital can be written as a linear combination of the wavefunctions for the individual atomic orbitals
What is Ca and Cb?
Numerical co-efficients which make the integral of Ψ2 = 1
How is a molecular orbital calculated?
Adding together appropriate contributions of all relevant atomic orbitals
The interactions between atomic orbitals are …
Allowed if the symmetries of the atomic orbitals are comparable Efficient if the region of overlap between the atomic orbitals is significant Efficient if the atomic orbitals are relatively close in energy
What is the energy like in a bonding orbital?
Lower from the energies of the atomic orbitals from which it is formed
What does the sign and value of an overlap integral depend on?
Size, shape, orientation and phase of atomic orbitals
What can the values of overlap integral be?
Negative Positive Zero
What is a positive overlap integral?
Determined by symmetry Lobes of the same phase come together
What is a negative overlap integral?
Lobes of different phase come together
What does a negative overlap integral represent?
Antibonding contribution orbital
What does a positive overlap integral represent?
Bonding contribution orbital
What is the energy like in an antibonding orbital?
Higher than bonding contributions
What is a zero orbital overlap?
there is an equal overlap and positive overlap so they cancel each other out
What does a zero orbital overlap represent?
Non-bonding contribution
What is the energy like in a non-bonding orbital?
No change in energy