structure, bonding and physical properties

Question 1

What structure does a metallic substance have?

Answer 1

giant metallic lattic

Question 2

What structure does an ionic substance have?

Answer 2

giant ionic lattice structures

Question 3

What structures does a covalent substance have?

Answer 3

giant covalent lattice structure
simple covalent lattice structure

Question 4

What is a giant metallic lattic structure?

Answer 4

metal atoms form a lattice held together by metallic bonding

Question 5

Describe metallic bonding in terms of electrons and orbitals.

Answer 5

the outer orbitals of the metal atoms overlap to some extent, so the metal can be thought of a lattice of positive ions surrounded by a ‘sea’ of delocalised electrons

Question 6

What is metallic bonding?

Answer 6

the attraction between a lattice of positive metal ions and a sea of delocalised electrons

Question 7

Why are metals good conductors of electricity?

Answer 7

the delocalised electrons are mobile
the more delocalised electrons there is the higher the conductivity

Question 8

Why do metals have a relatively high melting point?

Answer 8

a lot of energy is needed to break the strong metallic bonding
more delocalised electrons = the stronger the bond

Question 9

What are the key physical properties of metals?

Answer 9

conduction of heat, malleable, ductile, shiny, sonorous

Question 10

How is the structure maintained in a giant metallic lattice?

Answer 10

the positive charges repel each other which keeps the cations fixed in position

Question 11

What affects the BP and MP in giant metallic lattices?

Answer 11

the charge of the cations and the size of the cations
the larger the atomic radius = lower MP

Question 12

Why are metallic lattices insoluble in water?

Answer 12

the polar H2O and the charges in the metallic structure would lead to a reaction rather than dissolving

Question 13

How can you strengthen metals?

Answer 13

increase delocalised e-
increase positive charge of metal atoms
decrease the size of metal ions = tigher lattice

Question 14

What is a giant ionic lattice?

Answer 14

alternating arrangement of positive and negative ions

Question 15

What is the bond in a giant ionic lattice?

Answer 15

electrostatic attraction between oppositely charged particles

Question 16

Why do giant ionic substances have a high MP and BP?

Answer 16

lots of energy needed to break string ionic bonds
if the charge increases then the bond strength also increases

Question 17

Why are giant ionic lattices soluble in water?

Answer 17

the water can form ion-dipole forces with dissolved ions to compensate for the loss of ionic bonds

Question 18

Why can giant ionic lattices conduct electricity when molten or aqueous?

Answer 18

the ions are mobile

Question 19

What are covalent substances?

Answer 19

mainly non-metallic elements and compounds involing only non-metals

Question 20

Which type of covalent structure is more common?

Answer 20

simple molecular

Question 21

What are simple molecular structures?

Answer 21

each molecule is made up of a defined no. of atoms, covalently bonded together. the molecules are attracted together by intermolecular forces

Question 22

Why do simple molecular substances have a low MP and BP?

Answer 22

only the intermolecular forces have to be broken which are relatively weak
the covalent bonds are strong but they remain intact - has no affect

Question 23

Why do simple molecular substances have a low electrical conductivity?

Answer 23

they have no mobile electrons or ions

Question 24

Usually simple molecular structures have low solubility in water, what 2 conditions make them more soluble in water?

Answer 24

1. they react with water to form ions eg: hydrogen chloride —> H+ and CL-
2. they can form hydrogen bonds with water

Question 25

What allows simple molecular substances to form h bonds with water?

Answer 25

some of the hydrogen bonds between water molecules need to be broken the energy needed for this endothermic process comes from the exothermic process of forming H bonds at the same time

Question 26

What simple molecular compounds have high solubility in water?

Answer 26

compounds with OH or NH groups

Question 27

What is a giant covalent structure?

Answer 27

the covalent bonds extend throughout the whole crystal, usually in three dimensions

Question 28

Why do giant covalent lattices have high MP and BP?

Answer 28

due to covalent bonds acting in all directions and they need to be broken

Question 29

Describe diamond's structure

Answer 29

each carbon atom is covalently bonded to 4 other carbon atoms tetrahedral - 109.5

Question 30

What are diamond's properties?

Answer 30

very high MP = C-C bonds need to be broken very hard = giant lattice holding atoms together non-conductor = no mobile electrons or ions

Question 31

What are diamond's uses?

Answer 31

drill bits saw blades jewellery

Question 32

Describe Graphite's structure?

Answer 32

the covalent bonding only extends in two dimensions, giving layers which are held together by induced dipole- dipole forces each c atom is bonded to 3 other c atoms - arranged in a hexagon trigonal planar

Question 33

What are the properties of graphite?

Answer 33

layers can slide - weak d-d forces high MP = covalent bonds need to be broken delocalised electrons move freely within a layer = conducts electricity

Question 34

What are graphite's uses?

Answer 34

lubricants pencils

Question 35

Describe the structure of graphene?

Answer 35

iduvidual layers of hexagonal rings of 6 c atoms each c atom is bonded to 3 other c atoms trigonal planar

Question 36

What are the properties of graphene?

Answer 36

high tensile strength very high electrical conductivity high MP

Question 37

What are the uses of graphene?

Answer 37

biomedicene - drug delivery electronics membranes for cleaning water

Question 38

What bonding type is found in groups 1-3?

Answer 38

giant metallic

Question 39

What bonding types are found in groups 4-7?

Answer 39

giant covalent

Question 40

What bonding type is found in group 8?

Answer 40

simple molecular

Question 41

Why is the melting point of Be higher than Li?

Answer 41

Be has more outer shell electrons therefore more delocalised electrons per atom = metallic bonding is stronger

Question 42

Why does carbon have a higher Mp than Boron?

Answer 42

C has 4 covalent bonds per atom B only has 3 covalent bonds per atom more energy needed in C

Question 43

Why do N,O,F and Ne have low MP?

Answer 43

they are simple molecular only london forces need to be broken

Question 44

Why does neon have a lower MP and BP than N,O and F?

Answer 44

the other simple molecular elements are diatomic neon exists as induvidual atoms - fewer electrons and smaller SA for contact with other atoms fewer and weaker london forces

Question 45

Which element forms an octrahedral molecule with flourine?

Answer 45

sulfur

Question 46

Do ionic bonds have any intermolecular forces?

Answer 46

NO none

Question 47

Which is stronger ionic bonding or covalent bonding?

Answer 47

ionic

Question 48

What type of structure are these molecules? SiCl4 PCl3 SCl2

Answer 48

simple covalent

Question 49

Why does the boiling point increase of a polymer when you add more repear units?

Answer 49

more surface interaction so stronger london forces

Question 50

What is a sigma bond?

Answer 50

the overlapp of orbitals between atoms