Aman Bansal
Last Activity: 13 Years ago
Dear Radhakrishna,
Principles of Molecular Orbital Theory
| Principle | Details/Examples |
1 |
total number of molecular orbits is equal to the total number of atomic orbitals from combining atoms
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The molecule H2 is composed of two H atoms. Both H atoms have a 1s orbital, so when bonded together, there are therefore two molecular orbitals.
|
2 |
Bonding molecular orbitals have less energythan the constituent atomic orbitals before bonding
Antibonding molecular orbitals have more energy than the constituent atomic orbitals before bonding.
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Bonding molecular orbitals help stabilize a system of atoms since less energy is associated with bonded atoms as opposed to a system of unbound atoms.
Likewise, antibonding molecular orbitals cause a system to be unstabilized since more energy is associated with bonded atoms than that of a system of unbound atoms.
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3 |
Following both the Pauli exclusion principle and Hunds rule, electrons fill in orbitals of increasing energy.
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Electrons fill orbitals with the lowest energy first. No more than 2 electrons can occupy 1 molecular orbital at a time. Furthermore, all orbitals at an energy level must be filled with one electron before they can be paired. (see second diagram below) |
4 |
Atomic orbitals are best formed when composed of atomic orbitals of like energies.
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Molecular Orbital Configuration of Li2:
(s1s)2(s*1s)2(s2s)2
The bonding (s1s)2 and antibonding (s*1s)2 cancel each other out, leaving (s2s)2 as the valence electrons involved in the atoms bonding.
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Best Of luck
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Aman Bansal
Askiitian Expert