MOTheory - Bonding in molecules and solids Where were...

Bonding in molecules and solids
How are atoms held together in molecules and solids?
How does this contribute to the properties of a molecule or solid?
Magnetism (unpaired vs. paired electrons)
Electrical (metals, semiconductors, insulators)
Mechanical (hardness, strength)
Thermal (melting / boiling / decomposition)
Where we’re heading: The chemistry of modern materials
(extended solids), after a brief look at some key aspects of
bonding in molecules (molecular orbitals)
Bonding in Materials 1

Lewis dot structure for O
2
Are the electrons paired or unpaired?
Based on this structure: would you predict O
2
to be
paramagnetic or diamagnetic ?
Fractional Distillation of O
2
from air
Air contains (by volume):
78.08% N
2
(bp = 77 K) 0.93% Ar
20.95% O
2
(bp = 90 K) 0.038% CO
2
What is happening in the experiment?
What does this tell us about the Lewis dot structure of O
2
?
Bonding in Materials 2

Review of Covalent Bonding
• Each orbital holds 2 electrons
Orbital
probability of finding an electron
Energy of electron:
energy needed to remove an electron from the orbital
Bonding in Materials 3