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UNIT 9: Geometry, bonding theories - Coggle Diagram
UNIT 9: Geometry, bonding theories
UNIFYING IDEAS!
Lewis structures tell one the 2D arrangement of atoms and how the electrons will associate themselves (VSEPR acro)
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Valence-bonding theory uses electron domains to (hybridized) orbitals and concept of bonding/nonbonding electrons (full/half full orbits). Orbitals OVERLAP to form bonds
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VSEPR
Each bond, multiple bond, or lone pair is one electron DOMAIN.
Each domain is like a balloon attached to a center... they will try to space out as much as possible
For ABx atoms, there are typical geometries: 2: N/A, 3: Linear, 4: Tetrahedral, 5: Trigonal bipyramidal, 6: Octahedral
These geometries first apply to electron-domains, then the lone pairs are not considered in molecular geometry
Valence-Bonding
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hybridized orbitals occur when electrons elevate themselves, then s, p, or d orbitals COMBINE to form x equivalent hybridized orbitals
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Sigma bonds are bonds that connect atom-atom, but pi bonds are every other bond in a multiple bond, and form from half-filled p orbitals whose lobes stick out 90 deg. from plane
All hybridized orbitals are equal... all they want to do is get 2 electrons. So lone pairs can also occupy them
Extra info:
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When lone pairs are present in trigonal bipyramidal, they will occupy equatorial positions (farthest away from all others... most room to expand)
Nonbonding pairs and multiple bonds are more repulsive, decreasing bond angles around it.
When bonds are equal in molecules, it's assumed that they are at equal energies... this necessitates equal orbitals (hybridized)
Polarity:
Ionic vs. covalent, Polar vs. nonpolar, cancelling/noncancelling
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Bond dipoles express a separation of charges (partial charges when atoms are more/less electronegative.)