molecular orbital theory (what is it??) better bonding model than valence bond theory electrons...
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Molecular Orbital Theory
Molecular Orbital Theory
(What is it??)
Better bonding model than valence bond theory
Electrons are arranged in “molecular orbitals”
Dealing with valence shell electrons
Molecular Orbitals
Combination of atomic orbitals 2 atomic orbitals------2 molecular orbitals
Molecular region where electrons are likely to be found within a chemical compound
Behave like molecules
Deals with electrons arranged in molecules, NOT atoms
Bonding Molecular Orbital (σ)
Contain electrons involved in chemical bonding Contribute to bond strength Increase stability
Lower energy level for electrons
Increased electron density between atoms
Anti-bonding Molecular Orbitals (σ*)
Contain electrons NOT involved in bonding Electrons hang out away from bond Decreased stability and bond strength
Higher energy level for electrons
Decreased electron density between atoms
**Electrons want to be at a LOW energy level SO---generally pair up and reside in bonding molecular orbitals.
How are electrons placed in molecular
orbitals? 1) Electrons want to be in the lowest-energy
molecular orbitals as possible.
2) Only 2 electrons found in each molecular orbital.
3) Electrons are placed in molecular orbitals by themselves (parallel spins) unless they have to be paired up (opposite spins).
Bond Order
Determined by molecular orbitals
= (# electrons in bonding MO) – (# electrons in anti-bonding MO)
2
Example 2: Molecular orbital energy-level
diagram
H2+
What happens when “p” atomic orbitals
combine? Each “p” orbital combines with another “p” orbital—2
molecular orbitals produced
Of the 2 molecular “p” orbitals— 1 lower energy bonding orbital 1 higher energy anti-bonding orbital
One p orbital produces orbital overlap σp , σ*p
Other 2 p orbitals overlap in parallel πp , π*p
Example 3: O2
Homework
Read pp. 417-418
Problems #61, 63, 67
Read over Thursday lab procedure