Bonding

Question 1

State the type of bonding that forms between sodium and chlorine, and describe the structure formed? [2]

Answer 1

ionic bonding 1

giant ionic lattice 1

Question 2

Explain why ionic compounds tend to have a high melting point? [2]

Answer 2

strong electrostatic attractions 1

between oppositely charged ions 1

Question 3

Explain how each ion in MgCl2 is formed? [2]

Answer 3

(Mg) loses two electrons, to form Mg [2+] 1

each (Cl) gains one electron, to form Cl- 1

Question 4

Fully explain the electrical conductivity of sodium chloride, with reference to different states? [4]

Answer 4

(solid) CANNOT conduct electricity 1
ions are not free to move around 1

(molten) CAN conduct electricity 1
ions can move through structure and carry a current 1

Question 5

State the type of bonding that forms between two metals, and explain why they are strong? [2]

Answer 5

metallic bonding 1

attraction between positive ions and the sea of delocalised electrons 1

Question 6

Pure metals are often very malleable, explain why? [2]

Metal alloys are less malleable than pure metals. Describe how an ‘alloy’ is formed and explain why this gives them this property? [2]

Answer 6

particles arranged in regular layers 1
layers can slide over each other easily 1

different sized particles are added 1
distorts the layers, (harder for layers to slide) 1

Question 7

Explain why metallic structures are able to conduct electricity? [2]

Answer 7

delocalised electrons 1

can move through structure, and carry a current 1

Question 8

Explain why potassium has a lower melting point than sodium? [2]

Answer 8

[DOWN A GROUP ]
(K) is larger than Na 1
has a lower charge density 1

Question 9

Explain why magnesium has a higher melting point than sodium? [2]

Answer 9

[ACROSS A PERIOD]
(Mg) has more delocalised electrons 1
so stronger attraction to positive ions 1

Question 10

State the type of bonding present in silver, and draw a diagram to show the arrangement of particles? [3]

Answer 10

metallic bonding 1

( + ) ( + ) ( + ) positive ions 1
( + ) ( + ) ( + ) regular arrangement 1
( + ) ( + ) ( + )

Question 11

Describe what a covalent bond is? [1]
Draw a dot cross diagram to show the covalent bonds in a molecule of water? [1]
Give the name for the structure shown? [1]

Answer 11

shared pair of electrons 1
x x
o o
H O H
x x 1
x x
simple molecular 1

Question 12

Diamond is a substance used for its property of hardness and strength
Explain why diamond is hard? [2]

Answer 12

it is macromolecular 1

every carbon atom is bonded to four others 1

Question 13

Explain why both diamond and graphite have high melting points? [3]

Answer 13

have macromolecular structure 1
strong covalent bonds between carbon atoms 1
have a lot of energy to break 1

Question 14

What type of structure is shown by graphite? [1]

Explain why graphite can be used as a lubricant? [2]

Answer 14

giant covalent structure 1

layers are held together by weak van der Waals 1
layers can easily slide past each other 1

Question 15

Explain why graphite is good at conducting electricity? [3]

Answer 15

each carbon bonded to three others,
so each carbon has one delocalised electron 1

delocalised electrons are free to move 1
carry current through layers 1

Question 16

Graphite is used in for making pencils

Describe and explain a property that makes it ideal for this use? [2]

Answer 16

it is insoluble 1

covalent bonds are too strong to break 1

Question 17

Name the crystal type in an iodine crystal? [1]

Explain why solid iodine vaporises when it is warmed gently? [2]

Answer 17

molecular 1

van der Waals are weak 1
between iodine atoms 1

Question 18

Define the term ‘ dative covalent bond’? [2]

Describe what the arrow in a dative covalent bond represents? [1]

Answer 18

both electrons in a covalent bond 1
come from same atom 1

direction of electron transfer 1

Question 19

In terms of structure explain why a molecule of CH4 has no overall polarity? [2]

Answer 19

tetrahedral 1

gives it symmetry (charges cancel out) 1

Question 20

Explain why PH3 has greater boiling point than that of CH4? [3]

Answer 20

(PH3) is a trigonal pyramidal 1
has permanent dipoles between atoms 1

(CH4) has van der Waals, that require less energy to overcome 1

Question 21

Name the shape, and give a value for the bond angle in BF3 and PF3? [2]

Explain why they have different bond angles despite having the same number of bonding pairs? [3]

Answer 21

(BF3) trigonal planar = 120’ 1
(PF3) trigonal pyramidal = 107’ 1

(PF3) has a lone pair 1
electrons repel each other as far as possible 1
pushes the bonding pairs closer together 1

Question 22

Using the VSEPR theory, deduce the shape of the molecule NH3 and draw it? [2]

Answer 22

no. of outer e- (N) = 5
electrons from bonds = 3
(5 + 3) = 8 3 bond pairs 1
1 lone pair
H
\
H — N :
/ 1
H

Question 23

Deduce the shape of SF4, and give values for the bond angles present? [3]

Answer 23

(S) = 6
electrons from bonds = 4 1
(6 + 4) = 10 4 bond pairs
1 lone pair
seesaw 1
87’ and 102’ 1

Question 24

Deduce the shape of NH4 +, and give a value for the bond angle present? [2]

Answer 24

[N] = 5
electrons from bonds = 4
(5 + 4) = 9 (+ve charge) = 8 4 bond pairs

tetrahedral 1
109.5’ 1

Question 25

Water is a very important molecule
Deduce the shape of a H2O molecule, and draw the structure? [2]
Deduce a value for the bond angle? [1]

Answer 25

(O) = 6
electrons from bonds = 2
(6 + 2) = 8 2 bond pairs
2 lone pairs
bent shape 1
xx xx
O
/ \
H H
104.5’ 1

Question 26

Define the term ‘electronegativity’ ? [2]

Answer 26

power of an atom to attract a a pair of electrons 1

in a covalent bond 1

Question 27

Describe and explain what a dipole is? [2]

Describe how a polar bond is formed? [1]

Answer 27

a difference in charge 1
caused by, shift in charge density 1

Difference in electronegativity 1

Question 28

Explain how van der Waals cause atoms to be attracted to each other? [3]

Answer 28

electrons in charge clouds move quickly 1
form a temporary dipole 1
dipoles in opposites directions are attracted to each other 1

Question 29

in terms of intermolecular forces, explain why a molecule of C4H10 has a higher boiling point than that of C3H8? [2]

Answer 29

More electrons / larger molecule 1

Stronger van der Waals 1