Bailey N
Chapter 6 - VSEPR, hybridization, valence bond theory, molecular bond theory
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Briefly explain VSEPR theory
The different repulsions of electron groups (single/double/triple bonds) around the central atom determines the shape of the molecule
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Briefly explain lone pair effect
Lone pair groups take up more space than bonded electron groups, meaning they push bonding pairs together and effect the 'ideal' geometry of a molecule
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Steps for determining the geometry of a molecule using VSEPR
1) Draw the Lewis structure
2) Determine the electron geometry by counting the number of electron groups around the central atom (no matter how many bonds are in a bonding area it's still only 1 group)
3) Determine the molecular geometry by counting the number of bonded vs. lone pair groups and choose the correct group from the table
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geometry and bond angle for 2 electron groups
Linear
180°
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geometry and bond angle for 3 electron groups
Trigonal planar
120°
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geometry and bond angle for 4 electron groups
Tetrahedral
109.5°
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geometry and bond angle for 5 electron groups
Trigonal bypyramidal
120 and 90°
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geometry and bond angle for 6 electron groups
Octahedral
90°
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Steps for determining if a whole molecule is polar/nonpolar
1) Draw the Lewis structure
2) Determine if the molecule has polar bonds between individual atoms
3) Draw vector arrows from the least EN atom(s) to the most EN atom
4) Draw a line of symmetry along an axis of the molecule (usually up and down), determine if the bonds 'cancel' each other out of if they have a net dipole
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General rules for determining if a molecule is polar/nonpolar (3)
- Symmetrical molecules with the same type of atom/element surrounding the central atom = usually nonpolar
- Asymmetrical molecules with different atoms/elements surrounding the central atom = usually polar
- If the central atom has a lone pair = usually polar
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Hybridization
When standard atomic orbitals combine or overlap to form new, hybrid orbitals
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The number of standard atomic orbitals combined is ___ the number of hybrid orbitals created
- # atomic orbitals combined = # of hybrid orbitals created
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Characteristics of a sigma bond (3)
- Happens when two orbitals overlap end-to-end
- All single bonds are sigma bonds
- Double and triple bonds still have at least 1 sigma bond in them
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Characteristics of a pi bond (2)
- Happens when two p orbitals overlap side-to-side
- Only occur in double bonds or more
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Orbitals involved in sp hybrids
1 s and 1 p orbitals (2 leftover p)
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Orbitals involved in sp2 hybrids
1 s and 2 p orbitals (1 leftover p orbital)
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Orbitals involved in sp3 hybrids
1 2s and 3 2p orbitals
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Orbitals involved in sp3d hybrids
1 s, 3 p, and 1 d orbitals
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Orbitals involved in sp3d2 hybrids
1 s, 3 p,and 2 d orbitals
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Steps for determining hybrid orbitals
1) Draw the Lewis structure
2) Use VSEPR to determine electron groups
3) based on the number of electron groups (INCLUDING lone pairs) around the atom of interest, determine the geometry of the molecule and hybrid orbitals involved
4) write the bonding scheme for each bond
5) label bonds on molecule if asked
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Formula for determining molecular orbital bond order
(# of bonding electrons - anti-bonding electrons) ÷ 2
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The higher the bonding order the ___ and more ___ the bond
- stronger
- more stable
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A negative or 0 bond order results in an ___ or ___ bond
- unstable or no
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When writing a molecular configuration you should always include ___ in front of the bonds/bond types
- The noble gas configuration of the given element
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Hybrid orbitals of an atom in a molecule that corresponds with having electron groups 2-6
2 e.g = sp hybrids
3 e.g = sp2 hybrids
4 e.g = sp3 hybrids
5 e.g = sp3d hybrids
6 e.g = sp3d2 hybrids
