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CHEM - 2.2.2 Shape of Molecules and Intermolecular Forces > Shapes of Molecules and Ions > Flashcards

Flashcards in Shapes of Molecules and Ions Deck (9)
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1

What is the Electron Pair Repulsion theory?

- The groups of electrons surrounding the centre atom of a molecule determines it's shape
- Electrons will repel each other so that they are as far apart as possible
- Different numbers of electron groups result in different 3D shapes

2

Linear

No. of Bonded groups = 2
Bond Angle = 180
No. of Lone pairs = 0

3

Trigonal Planar

No. of Bonded groups = 3
Bond Angle = 120
No. of Lone pairs = 0

4

Tetrahedral

No. of Bonded groups = 4
Bond Angle = 109.5
No. of Lone pairs = 0
Eg. CH4

5

Trigonal Pyramidal

No. of Bonded groups = 3
Bond Angle = 107
No. of Lone pairs = 1
Eg. NH3

6

Octahedral

No. of Bonded groups = 6
Bond Angle = 90
No. of Lone pairs = 0

7

Non-linear

No. of Bonded groups = 2
Bond Angle = 104.5
No. of Lone pairs = 2
Eg. H2O

8

Trigonal Bipyramidal

No. of Bonded groups = 5
No. of Lone pairs = 2

9

Bonded-pair and lone-pair repulsions

- Lone pairs repel more strongly as they are closer to the central atom and they occupy more space.
- Bond angle is reduced by about 2.5 degrees for each lone pair