๐Ÿ“š

All Subjects

ย >ย 

๐Ÿงชย 

AP Chem

ย >ย 

๐Ÿค“

Unit 2

2.7 VSEPR, Bond Hybridization, and Molecular Geometry

3 min readโ€ขaugust 23, 2020

Anika P

dalia

Dalia Savy

fiveable-dylan

Dylan Black


AP Chemistryย ๐Ÿงช

Bookmarkedย 6.5kย โ€ขย 251ย resources
See Units

Valence Shell Electron Pair Repulsion (VSEPR)

Lewis structures can determine properties such as geometry, bond orders, bond lengths, and dipoles for molecules. The Valence-Shell-Electron-Pair-Repulsion (VSEPR) theory can predict molecular geometry by minimizing electron electron repulsion.

Notes

You should definitely memorize the table below for the AP Exam. Once you practice, the questions that involve the VSEPR Theory become free points๐Ÿฅณ!
Let's go over what each column means:
  • Family - think of family as how many groups of atoms or molecules branch off the middle atom (number of x + number of e in the general formula).
  • General Formula - made up of three parts:
    • M = middle atom
    • X = attached atoms
    • E = lone pairs
  • Electron Domain Geography - gives you an idea of what the molecule looks like. It shows where the electrons or atoms are in relation to the middle atom, M.
    • The graph below also includes angle measures that you should be aware of.
  • Shape - This is the main column that you should memorize and learn to associate with the general formula, electron domain geography, and hybridization.
  • Hybridization - You only have to memorize the hybridization of family 2, 3, and 4๐Ÿง .

VSEPR

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-3XYkaKD1EK6C.JPG?alt=media&token=1b6ca71e-60aa-47d9-ab0e-1d306134874b
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-Pk7lkst15jER.JPG?alt=media&token=55401b80-d48d-48c4-9405-bff1deb123d4
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-ztmzKNevvgAd.JPG?alt=media&token=238e06fb-b185-48df-a91d-4daa89c6b19d
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-uSiziRLhLDrZ.JPG?alt=media&token=f37d0881-7d68-4398-9836-d947be72d419

Bonding

Sigma and Pi Bonds

Sigma (ฯƒ) bonds are covalent bonds where electrons are found shared on the internuclear axis. Hybrid orbitals form ฯƒ bonds, and they are stronger than ฯ€ bonds.
Pi (ฯ€) bonds are covalent bonds where orbitals are perpendicular๐Ÿ“ to the internuclear axis. Unhybridized orbitals form ฯ€ bonds.
You don't really have to know these definitions, but be aware of the following:
  1. A single bond is made up of 1 ฯƒ bond.
  2. A double bond is made up of 1 ฯƒ bond and 1 ฯ€ bond.
  3. A triple bond is made up of 1 ฯƒ bond and 2 ฯ€ bonds.
The more pi bonds in a molecule:
  • The higher the bond energy
  • The shorter the bond length

Examples

Count the number of ฯƒ bonds and the number of ฯ€ bonds in the following two structures:
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-keZIajahD1YR.jpg?alt=media&token=4b6d4124-c57e-452e-8b94-bd9c17ce57dd

Image Courtesy of BC Open textbooks

In the molecule on the left, there is 1 triple bond and 2 single bonds. 1 triple bond is made up of 1 ฯƒ bond and 2 ฯ€ bonds, while the single bond is only made up of 1 ฯƒ bond. Therefore, in total, there are 3 ฯƒ bonds and 2 ฯ€ bonds in this molecule.
In the molecule on the left, there are 3 double bonds and 9 single bonds. This means this molecule is made up of 12 ฯƒ bonds and 3 ฯ€ bonds.

Hybridization

Hybridization is the idea that atomic orbitals fuse to form newly hybridized orbitals, which in turn, influences molecular geometry and bonding properties. Hybridization is also an expansion of the valence bond theory๐Ÿ’ฅ.
There are 5 main hybridizations, 3 of which you'll be tested on: sp3, sp2, sp, sp3d, sp3d2. For these hybridizations, electron orbitals fuse together to fill subshells and go to a lower energy state. It also allowed for things like CH4, since technically the way the electron pairs are organized, 4 sigma bonds would not be possible.
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-Mgor06egZJrH.jpg?alt=media&token=6084b719-cbb4-4bef-a175-9bc5d9c445b8
In the above example, carbon's 2p and 2s orbitals fuse into 4 half filled sp3 orbitals that can make 4 sp3-orbital sigma bonds. The same principle applies for the other hybridizations.

Was this guide helpful?

Fiveable logo
Join Fiveable for free
Create a free account to bookmark content and compete in trivia
Hours Logo
Studying with Hours = the ultimate focus mode
Start a free study session
Browse Study Guides By Unit
๐Ÿ“†Big Reviews: Finals & Exam Prep
โœ๏ธFree Response Questions
โœ๏ธFrequently Asked Questions
๐ŸงMultiple Choice Questions
โš›๏ธUnit 1: Atomic Structure and Properties
๐Ÿค“Unit 2: Molecular and Ionic Compound Structures and Properties
๐ŸŒ€Unit 3: Intermolecular Forces and Properties
๐ŸงชUnit 4: Chemical Reactions
๐Ÿ‘ŸUnit 5: Kinetics
๐Ÿ”ฅUnit 6: Thermodynamics
โš–๏ธUnit 7: Equilibrium
๐ŸŠUnit 8: Acids and Bases
๐Ÿ”‹Unit 9: Applications of Thermodynamics
FREE AP chem Survival Pack + Cram Chart PDF
Sign up now for instant access to 2 amazing downloads to help you get a 5
๐Ÿ“ฑ Stressed or struggling and need to talk to someone?
Talk to a trained counselor for free. It's 100% anonymous.
Text FIVEABLE to 741741 to get started.
ยฉ 2021 Fiveable, Inc.