Bonding: Shapes of Molecules Flashcards
1
Q
Regular Shapes
A
• Linear
- 2 bonding pairs
- 180º
• Trigonal planar
- 3 bonding pairs
- 120º
• Tetrahedral
- 4 bonding pairs
- 109.5º
• Trigonal bipyramidal
- 5 bonding pairs
- 90º & 120º
• Octahedral
- 6 bonding pairs
- 90º
2
Q
Central Atoms with 2 Charge Clouds
A
• Linear
- 2 bonding pairs
- 180º
3
Q
Central Atoms with 3 Charge Clouds
A
• Trigonal planar
- 3 bonding pairs
- 120º
- Repulsion of charge clouds are the same between each pair so the bond angles are all 120º
• Bent
- 2 bonding pairs, 1 lone pair
- Little bit less than 120º
4
Q
Central Atoms with 4 Charge Clouds
A
• Tetrahedral
- 4 bonding pairs
- 109.5º
• Trigonal pyramidal
- 3 bonding pairs, 1 lone pair
- 107º
- The increased repulsion of the lone pair pushes the bonding pairs closer together, reducing the bond angle to 107⁰ from 109.5⁰
• Bent
- 2 bonding pairs, 2 lone pairs
- 104.5⁰
- The more lone pairs, the greater the distortion to the bond angle
5
Q
Central Atoms with 5 Charge Clouds
A
• Trigonal bipyramidal
- 5 bonding pairs
- 90º & 120º
• Seesaw
- 4 bonding pairs, 1 lone pair
- 102º & 86.5º or <90º & <120º
• T-shaped
- 3 bonding pairs, 2 lone pairs
- <90º
6
Q
Central Atoms with 6 Charge Clouds
A
• Octahedral
- 6 bonding pairs
- 90º
• Square pyramidal
- 5 bonding pairs, 1 lone pair
- 90º
• Square planar
- 4 bonding pairs, 2 lone pairs
- 90º
7
Q
Working out the shape of a molecule
A
- Find the central atom
- Work out how many electrons are in the outer shell of the central atom. This will be the same as the element’s group number
- Add 1 electron for every atom that the central atom is bonded to
- If looking at an ion, add 1 electron for each negative charge or subtract 1 electron for each positive charge
- Add up all electrons, divide by 2 to find the number of electron pairs
- Compare the number of electron pairs to the number of bonds to find the number of lone pairs and the number of bonding pairs on the central atom
