Download VSEPR Molecular Geometry VSEPR Molecular Geometry

11/18/2009
Chemistry 25
VSEPR
Molecular Geometry
Chemistry 25
VSEPR
Molecular Geometry
Quantum Chemistry
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11/18/2009
Quantum Numbers, QN

Orbitals
•
Principal QN, n
•
Angular momentum QN, l
• Shell, nth # of period
• Atomic size, energy
• Analogy: nth floor
• Whole number, 1, 2, 3, ….
• Sub-shell
• Shape of the sub-shells
•
Electron clouds, possibilities
of finding electrons (99%)
• 0, …, n-1
s
0
p
1
d
2
f
3
Quantum Numbers, QN

Orbitals (continue)
• Magnetic QN, ml .
• Orbitals, (# = 2 l + 1)
• ml:
-l ,-l +1, -l +2, …, 0, 1, 2, …,s l

Electrons
n= 3
l=0
l=1
l=2
m l = 0 m l = -1 m l = -2
0
-1
+1
0
+1
+2
p
d
• Spin QN, m
• ±1/2
f
2
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The filling of Electrons
s
p
d
f
The Filling of Electrons
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11/18/2009
Chemistry 25
VSEPR
Molecular Geometry
Lewis Dot Structure
Valence Shell/Electrons

Valence Shell
• The valence shell is the outermost shell of an
atom

Valence Electrons
• the outermost electrons of an atom
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Lewis Dot Structure

Octet rule
•

Atoms tend to gain, lose or share electrons so as to
have eight electrons in their outer electron shell.
Procedures
•
•
•
•
•
•
•
Add total # of valence electrons
Determine central atom, eletropositive element
Determine terminal/ peripheral atoms
Connect central and terminal atoms
Fulfill octet rule for terminal atoms
Add electron to the central atom
Determine the possibility of multiple bonds
Exception of Octet rule

Octet rule
• Atoms tend to gain, lose or share electrons so as
to have eight electrons in their outer electron
shell.

Exceptions
• Electron deficient
• Group I, II, III
• Electron deficient
• d, f orbitals involved
• Odd # of Electron
• Group V: N
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Molecular Geometry

sxpydzEn
•
•
•
s, p, d, are
sub-shell
x, y, z are #
of orbitals
occupied
N is # of lonepair or nonbonding
electron pairs
sp
sp2
sp3
sp3d
sp3d2
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