Chapter 5: Advanced Bonding Concepts

Valence bond theory

electrons in a molecule occupy orbitals of the individual atoms, bonds form when unpaired electrons in the valence shell atomic orbitals pair 

Orbital overlap

orbitals on two atoms overlap

Sigma bond

density concentrated along the intra-nuclear axis (between two nuclei)- hybrid orbitals and lone pairs 

Hybrid orbitals

combination of wave function of the same atom to form a new set of equivalent wave functions; a combination of all orbitals of an atom

Pi bond

overlap of p orbitals oriented perpendicularly to the inter-nuclear axis (two separate regions of electron density)

sp hybrids

-2 ED

-linear

sp² hybrids

-3 ED

-trigonal planar

sp³ hybrids

-4 ED
-tetrahedral

sp³d hybrids

-5 ED

-trigonal bi-pyramidal

sp³d² hybrids

-6 ED

-octahedral

Molecular orbit (MO) theory

mathematical function that describes the behavior of an electron in a molecule (forms from the overlap of atomic orbitals)

constructive interference

-bonding (σ)

-stabilizing, lowers energy

-amplitude increases

destructive interference

-anti bonding (σ*)

-increases energy’

-no amplitude (flat line)

Bond order

how stable a molecule is (adding an electron to bonding MO increases the BO, adding an electron to an anti-bonding MO decreases the BO)

Paramagentic

unpaired electrons, strongly attracted to the magnetic field

Diamagnetic

all electrons are paired, slightly repelled by the magnetic field)

Bond order vs bond type

1= single bond

2= double bond

3= triple bond

*BO can be fractional*