Shapes of molecules and ions

Question 1

The electron pair repulsion theory (EPR) states that:

Answer 1

the shape of a molecule or ion is caused by repulsion between the pairs of electrons, both bond pairs and lone (non-boning) pairs, that surround the central atom
the electron pairs arrange themselves around the central atom so that the repulsion between them is at minimum
lone pair-lone pair repulsion> lone pair-bond pair repulsion> lone pair-bond pair repulsion> bond pair-bond pair repulsion

Question 2

the lone pair to lone pair repulsion is……..than lone pair to bond pair repulsion

Answer 2

greater

Question 3

the lone pair to bond pair repulsion is…….. than bond pair to bond pair repulsion

Answer 3

greater

Question 4

the EPR theory is also called the

Answer 4

valence shell electron pair repulsion theory, VSEPR

Question 5

the first two rules of EPR are used to

Answer 5

obtain the basic shape of the molecule or ion

Question 6

the third rule of EPR is used to

Answer 6

estimate values for the bond angles

Question 7

to obtain the shape of a molecule or ion it is first necessary to

Answer 7

obtain the number of bond pairs and lone pairs of electrons around the central atom

Question 8

the best way to obtain the number of lone and bond pairs of electrons around the central atom is by

Answer 8

drawing a dot and cross diagram

Question 9

in order to determine the shape of a molecule containing one or more multiple bonds,

Answer 9

treat each multiple bond as if it contained only one pair of electrons

Question 10

the displayed formula for carbon dioxide is

Answer 10

O=C=O

Question 11

a carbon dioxide molecule has no

Answer 11

lone pairs on the carbon atom

Question 12

the seven shapes of molecules are

Answer 12

linear
trigonal planar
tetrahedral
trigonal bipyramical
hexagonal
trigonal pyramidal
V-shaped

Question 13

in linear molecules, eg BeCl2 the bond angle is

Answer 13

180°

Question 14

in trigonal planar molecules, eg BCl3the bond angle is

Answer 14

120°

Question 15

in tetrahedral molecules, eg CH4 the bond angle is

Answer 15

109.5°

Question 16

in trigonal pyramidal molecules, eg NH3, which has a lone pair of electrons, the bond angle is

Answer 16

107°

Question 17

in V-shaped molecules, eg H2O, which has two lone pairs, the bond angle is

Answer 17

104.5°

Question 18

in trigonal bipyramidal molecules, eg PCl5, the two bond angles are:

Answer 18

90° and 120°

Question 19

in hexagonal molecules, eg SF6, the two bond angles are

Answer 19

90° and 180°

Question 20

in tetrahedral ions, such as NH4+, the bond angle is

Answer 20

109.5°