1.6 shapes of molecues

Question 1

what does shape of molecule or ion depend on?

Answer 1

The shape of a molecule or ion depends on the number of pairs of electrons in the
outer shell of the central atom, and how they repel each other.

Question 2

The Valence Shell Electron Pair Repulsion (VSEPR) theory

Answer 2

The Valence Shell Electron Pair Repulsion (VSEPR) theory states that the pairs of electrons repel one another so that there is minimum repulsion between them.

Question 3

2 bonding pairs of electrons

Answer 3

Electron pairs repel each other. Two bonding pairs of electrons repel each other
equally and the molecule takes up linear shape to minimise repulsions.
Bond angle: 180o

Question 4

3 bonding pairs

Answer 4

Electron pairs repel each other. Three bonding pairs of electrons repel each other
equally and the molecule takes up trigonal planar shape to minimise repulsions.
Bond angle: 120o

Question 5

4 bonding pairs of electrons

Answer 5

Electron pairs repel each other. Four bonding pairs of electrons repel each other
equally and the molecule takes up tetrahedral shape to minimise repulsions.
Bond angle: 109.5o

Question 6

5 bonding pairs

Answer 6

Electron pairs repel each other. Five bonding pairs of electrons repel each other
equally and the molecule takes up trigonal bipyramidal shape to minimise repulsions.
Bond angles: 120o and 90o

Question 7

6 bonding pairs

Answer 7

Electron pairs repel each other. Six bonding pairs of electrons repel each other
equally and the molecule takes up octahedral shape to minimise repulsions.
Bond angle: 90o

Question 8

3 bonding pairs of electrons and 1 lone pair of electrons

Answer 8

Electron pairs repel each other. Three bonding pairs of electrons and one lone pair
of electrons. Lone pair of electrons has a greater repulsion and the molecule takes
up pyramidal shape to minimise repulsions.
Bond angle: 107o

Question 9

2 bonding pairs of electrons and 2 lone pairs of electrons

Answer 9

Electron pairs repel each other. Two bonding pairs of electrons and two lone pairs of
electrons. Lone pairs of electrons have a greater repulsion and the molecule takes
up bent shape to minimise repulsions.
Bond angle: 104.5o

Question 10

BrF4 -

Answer 10

Electron pairs repel each other. Four bonding pairs of electrons and two lone pairs
of electrons. Lone pairs of electrons have a greater repulsion and the molecule
takes up square planar shape to minimise repulsions.
Bond angle: 90o

Question 11

BrF3

Answer 11

Electron pairs repel each other. Three bonding pairs of electrons and two lone pairs
of electrons. The basic shape is trigonal bipyramidal but the lone pairs of electrons
have a greater repulsion than the bonding pairs of electrons and so the molecule
takes up T shape to minimise repulsions.
Bond angle: 86o

Question 12

XeF2

Answer 12

Electron pairs repel each other. Two bonding pairs of electrons and three lone pairs
of electrons. The basic shape is trigonal bipyramidal but the lone pairs of electrons
have a greater repulsion than the bonding pairs of electrons and so the molecule
takes up linear shape to minimise repulsions.
Bond angle: 180o