Bonding and Structure

Question 1

shape and angle for 2 bonding pairs

Answer 1

linear- 180 degrees

Question 2

shape and angle for 3 bonding pairs

Answer 2

trigonal planar-120 degrees

Question 3

shape and angle for 4 bonding pairs

Answer 3

tetrahedral- 109.5 degrees

Question 4

shape and angle for 5 bonding pairs

Answer 4

trigonal bipyramidal- 90 and 120 degrees

Question 5

shape and angle for 6 bonding pairs

Answer 5

octahedral- 90 degrees

Question 6

shape and angle for 3 bonding pairs + 1 lone pair

Answer 6

trigonal pyramidal, 107 degrees

Question 7

shape and angle for 2 bonding pairs + 2 lone pairs

Answer 7

bent, 104.5 degrees

Question 8

explanation for angles in a molecule

Answer 8

if there any state how many lone pairs there are
if lone pairs are present state that lp-lp repel more the bp-bp
electrons pairs arrange themselves around the central atom to minimise repulsion

Question 9

what causes London forces?

Answer 9

temporary asymmetrical electron distribution induces a dipole in adjacent molecule

Question 10

why does Mg have a higher melting point than Na

Answer 10

Mg has more delocalised electrons than Na
Mg2+ has a larger charge than Na+
Mg2+ is smaller than Na+
Mg’s delocalised electrons and cations have a stronger electrostatic attraction

Question 11

explanation for SHAPE of a molecule

Answer 11

state how many electron pairs there are

Question 12

why is cyclohexane not soluble in water?

Answer 12

cyclohexane can only form London forces

it wouldn’t be able form hydrogen bonds with water

Question 13

effect that branching has on a molecules boiling point?

Answer 13

decreases the surface area of contact for London forces to occur so boiling point has decreased

Question 14

why does water have a higher boiling point that expected?

Answer 14

water can form two hydrogen bonds per molecule because the oxygen has two lone pairs
stronger hydrogen bonding

Question 15

what effect does hydrogen bonding on density of ice compared to water?

Answer 15

ice has lower density than water
hydrogen bonds holds the molecules further apart
forms a tetrahedral arrangement

Question 16

physical properties of diamond

Answer 16

each carbon atom forms four covalent bonds (giant covalent structure)
cannot conduct electricity because all electrons are involved in bonding

Question 17

arrangement and physical properties of graphite

Answer 17

carbon atoms arranged in layers
3 localised electrons and 1 delocalised electron per carbon atom
the delocalised electron is mobile and carries charge throughout the structure

Question 18

Define ‘electronegativity’

Answer 18

The ability for an atom to attract a pair of electrons in a covalent bond

Question 19

why are metals malleable?

Answer 19

layers of ions can slide over each

electrons between the layers can prevent repulsion

Question 20

why are ionic solids brittle?

Answer 20

layers of ions are displaced when bent and the ions of the same charge line up and repel each other