Cheatography
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Hybridization
Formal Charge |
FC = (group #) - (loan pairs + bonds) |
Bond Enthalpy |
ΔHrxn = (sum of bonds broken) - (sum of bonds formed) |
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Weaker bonds broken provide more exothermic reactions. Weaker product bonds make for a less exothermic reaction. |
Bond Order and Length |
Shorter bond length = greater bond order |
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Single bonds are the longest and the weakest |
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Triple bonds are the shortest and the strongest |
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Non-integer bond order indicates resonance |
Non-polar covalent bonds |
ex: Cl-Cl |
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small energy difference in electronegativity |
Polar Covalent Bonds |
ex: H-Cl |
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medium energy difference |
Ionic Bonds |
ex: Li-Cl |
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large energy difference (over 1.7) |
Average Bond Order |
ABO = (# of bonds in the molecule) ÷ (# of resonance structures) |
MO Theory
MO diagram for F2, O2, Ne2, and all other molecules
MO Theory
Bond Order |
(bonds-antibonds) ÷ 2 |
Bonds |
σ, π |
Anti-Bonds |
σ, π |
Sigma Bond |
hybridized \ |
Pi Bond |
unhybridized p orbital \ |
Loan Pair |
Spin Paired \ --> X |
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VSEPR
Number of Electrons |
Electron Geometry |
Atoms + Loan Pairs |
Molecular Geometry |
2 |
linear |
2+0 |
linear |
3 |
trigonal planar |
3+0 |
trigonal planar |
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2+1 |
bent |
4 |
tetrahedral |
4+0 |
tetrahedral |
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3+1 |
trigonal pyramidal |
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2+2 |
bent |
5 |
trigonal bipyramidal |
5+0 |
trigonal bipyramidal |
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4+1 |
see-saw |
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3+2 |
T-shaped |
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2+3 |
linear |
6 |
octahedral |
6+0 |
octahedral |
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5+1 |
square pyramidal |
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4+2 |
square planar |
Polarity
Requirements for a Polar Molecule |
Bonds must be polar |
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The molecule cannot have symmetry |
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A bond is polar if one side is more electronegative than the other |
MO Theory
Diagram for B2, C2, and N2
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The Born-Haber Cycle
Sublimation |
Na (s) + 1/2 Cl2 (g) --> Na (g) + Cl (g) |
+107.32 kJ |
Cl-Cl bond energy |
Na (g) + Cl (g) --> Na (g) + 1/2 Cl2 (g) |
+121.68 kJ |
ionization energy of sodium |
Na (g) + 1/2 Cl2 (g) --> Na+(g) + Cl (g) + e- |
+496 kJ |
Electron Affinity of Cl |
Na+(g) + Cl (g) + e- --> Na+ (g) + Cl- (g) |
-349 kJ |
Lattice Energy of NaCl |
Na+ (g) + Cl- (g) --> NaCl (s) |
-786 kJ |
Sigma and Pi Bonds
Valence Bond Theory |
When two atoms are in close proximity to one another, they arrange themselves at the lowest possible energy |
Sigma bonds |
Formed by end-on overlap of orbitals along the internuclear axis |
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the electron density is highest right between the two atoms |
Pi bonds |
Formed by side on overlap of orbitals |
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there is no electron density between the atoms |
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Weaker than sigma bonds |
Valence electron pairs |
Electron Geometry |
Hybridization |
2 |
linear |
sp |
3 |
trigonal planar |
sp2 |
4 |
tetrahedral |
sp3 |
5 |
trigonal bipyramidal |
sp4 |
6 |
octahedral |
sp5 |
Single Bonds |
one sigma bond |
Double Bonds |
one sigma, one pi bond |
Triple Bonds |
one sigma, two pi bonds |
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