topic 2 recap Q. structure and bonding

Question 1

What is a covalent bond?

Answer 1

a shared pair of electrons

Question 2

which type of atoms form covalent bonds?

Answer 2

non-metals

Question 3

why do simple covalent substances not conduct electricity?

Answer 3

do not have delocalised electrons.

Question 4

describe the structure and bonding of small molecules

Answer 4

small molecules with strong covalent bonds between the atoms and weak intermolecular forces between molecules

Question 5

what is an ion?

Answer 5

an atom that has lost or gained electrons

Question 6

what charges do ions from group 1 and 2 form?

Answer 6

+1
+2

Question 7

why do small molecules have low melting points?

Answer 7

only a small amount of energy is needed to break the weak intermolecular forces

Question 8

what charges do ions from group 6 and 7 form?

Answer 8

2-
1-

Question 9

name the force that holds oppositely charged ions together?

Answer 9

electrostatic forces of attraction

Question 10

which kinds of elements form ionic bonds?

Answer 10

metals and non-metals

Question 11

describe the structure of a giant ionic lattice?

Answer 11

alternating positive and negative ions, held together by the electrostatic force of attraction

Question 12

why do ionic substances have high melting points?

Answer 12

the electrostatic force is strong and needs alot of energy to break

Question 13

why dont ionic substances conduct electricity when solid?

Answer 13

ions are in a fixed position so cannot move, and there are no delocalised electrons

Question 14

when can ionic substances conduct electricity?

Answer 14

when melted or dissolved

Question 15

why do ionic substances conduct electricity when molten or dissolved?

Answer 15

ions are free to move and carry charges

Question 16

describe the structure of a pure metal?

Answer 16

strong electrostatic forces of attraction between metal ions and delocalised electrons

Question 17

describe the bonding of a pure metal

Answer 17

layers of positive metal ions surrounded by delocalised electrons

Question 18

what are the four properties of pure metals?

Answer 18

malleable
high melting/boiling point
good conductors of electricity
good conductors of thermal energy

Question 19

explain why alloys are harder then pure metals

Answer 19

different sized atoms disturb the layers which prevents them from sliding over each other

Question 20

explain why pure metals are malleable

Answer 20

layers can slide

Question 21

explain why metals have high melting and boiling points

Answer 21

electrostatic forces of attraction between positive metal ions and delocalised electrons is strong

Question 22

why are metals good conductors of electricity?

Answer 22

delocalised electrons are free to move and carry charge

Question 23

why are metals good conductors of thermal energy?

Answer 23

delocalised electrons are free to move and transfer thermal energy

Question 24

what is an alloy?

Answer 24

a mixture of a metal with another element

Question 25

describe the structure and bonding of a giant covalent substances

Answer 25

billions of atoms bonded together by strong covalent bonds

Question 26

describe the structure and bonding of polymers

Answer 26

many identical molecules joined together by strong covalent bonds in a long chain, with weak intermolecular forces between the chains

Question 27

why do giant covalent substances have high melting points

Answer 27

it takes alot of energy to break the strong covalnt bonds

Question 28

explain why graphite is soft

Answer 28

layers are not bonded so they can slide over each other

Question 29

why do large molecules have higher melting and boiling points than small molecules?

Answer 29

the intermolecular forces are stronger

Question 29

why do most covalent substances not conduct electricity?

Answer 29

they do not have delocalised electrons or ions

Question 30

describe the structure and bonding in graphite?

Answer 30

each carbon atom is bonded to 3 others in a hexagonal ring arranged in layers. each atom delocalises one electron and the forces between layers are weak

Question 31

why can graphite conduct electricity

Answer 31

1 delocalised electron per carbon

Question 32

what is graphene

Answer 32

one layer of graphite

Question 33

give two properties of graphene

Answer 33

strong conducts electricity

Question 34

what is fullerene?

Answer 34

hollow cage of carbon atoms arranged in a sphere or tube

Question 35

what is a nanotube?

Answer 35

hollow cylinder of carbon atoms

Question 36

how big are nanoparticles?

Answer 36

1-100 nm

Question 37

give two properties of nanotubes

Answer 37

high tensile strength conduct electricity

Question 38

how are nanomaterials different from bulk materials?

Answer 38

nanomaterials have a higher surface area-to-volume ratio

Question 39

what is the relationship between side length and surface area-to-volume ratio?

Answer 39

as the side length decreases by a factor of 10 the surface area-to-volume increases by a factor of 10

Question 40

what are nanoparticles use for?

Answer 40

healthcare electronics cosmetics catalysts

Question 41

how big are fine particles?

Answer 41

100-2500 nm

Question 42

give 3 uses of fullerenes

Answer 42

lubricants drug delivery electronics

Question 43

how big are course particles?

Answer 43

2.5 x 10-6 to 1 x 10-5