C6.1 Shapes Of Molecules

Question 1

Electron-pair repulsion theory

Answer 1

Every electron has a negative charge, therefore repel
Model used to explain and predict shapes of mol and polyatomic atoms
-electron pairs determine shape (surrounding)
Electron pairs repel each other, so arranged far as possible, arrangement electron pairs minimises repulsion, holds atoms in definite shape
Diff no electron pairs result in diff shapes

Question 2

Shapes of molecules: wedges

Answer 2

solid line = bond in plane of paper
solid wedge = comes out of paper’s plane
dotted wedge = in plane of paper

Question 3

bonded and lone pair repulsions

Answer 3

lone pair = slightly closer central atom, occupies more space, lone pair repel more strong
bond - bond = bond - lone = lone - lone

Question 4

4 electron pair shape

Answer 4

4 electron pairs = tetrahedral arrangement, repel as far as can, lone pairs repel more strongly than bonded, angle reduced by 2.5 degrees per lone pair
Tetrahedral = 4 bonded = 0 lone = 109.5 bond angle

Question 5

Pyramidal shape

Answer 5

107 degree bonding angle
1 lone pair
3 bonded pair
Unequal distribution drawing

Question 6

Non linear shape

Answer 6

2 bonded pairs
2 lone pairs
104.5 degree bond angle
Greater number of electron pairs, smaller bond angle

Question 7

Linear shape

Answer 7

180 degree bond angle
2 electron pairs / regions
Co2

Question 8

Trigonal Planar

Answer 8

3 electron pairs / regions
120 degrees bond angle
Equal bond angles
Eg. Boron trifluoride BF3

Question 9

Octahedral

Answer 9

6 bond pairs / regions
90 degrees
eg. SF6
Equal bond angles