FC11: Structure & Bonding

Question 1

Describe the bonding in metallic substances

Answer 1

metallic bonding - electrostatic attraction between the positive metal ions and delocalised negative electrons

Question 2

What is the structure of metallic substances

Answer 2

giant metallic lattice

Question 3

What does the strength of a metallic bond depend on

Answer 3

the number of delocalised electrons per atom

Question 4

What is the trend in melting point in metals

Answer 4

as the number of delocalised electrons per atom increases, melting point increases, as more energy is needed to break the stronger metallic bonding

Question 5

What substances have simple molecular structure

Answer 5

covalent substances that do not have a giant covalent lattice structure

Question 6

what is the bonding in simple molecular substances

Answer 6

covalent

Question 7

what is the trend in melting points in simple molecular substances

Answer 7

As the total number of electrons increases, the strength of london forces between molecules increases, and so more energy is required to overcome the intermolecular forces, and so melting point increases as total number of electrons increases

Question 8

What is the bond or forces in simple molecular substances

Answer 8

intermolecular forces: hydrogen bonding, pd-d forces, london forces

Question 9

what substances have giant covalent structures

Answer 9

diamond, graphite, graphene, silicon, silica, boron

Question 10

what is the structure of diamond (describe no. of bonds around carbon atoms and shape)

Answer 10

4 covalent bonds around each carbon atom, tetrahedral shape

Question 11

what is the structure of graphite (describe no. of bonds around carbon atoms and shape)

Answer 11

3 covalent bonds around each carbon atom, trigonal planar shape

Question 12

how can graphite conduct electricity but not diamond

Answer 12

graphite has one delocalised mobile electron per atom, which can flow between the layers to carry a charge, whereas diamond cannot as all 4 of its outer electrons are involved in bonding

Question 13

explain the high electrical conductivity of graphite and graphene in relation to their structure, and also the strength of the structure

Answer 13

trigonal planar shape around each carbon atom, 3 covalent bonds per carbon therefore 1 electron remains unused, creating a sea of delocalised electrons giving them a high electrical conductivity. London forces holds the layers together which are weak (pencil)

Question 14

Describe the mpt/bpt of giant covalent substances

Answer 14

many strong covalent bonds which require a lot of energy to break, and so giant covalent substances have high melting and boiling points

Question 15

describe the bonding in substances with a giant ionic lattice structure

Answer 15

ionic bonding - electrostatic attraction between oppositely charged ions

Question 16

describe the mpt/bpt of giant ionic compounds

Answer 16

very high mpt/bpt, as a lot of energy is needed to break many strong ionic bonds

Question 17

explain the electrical conductivity of ionic compounds

Answer 17

cannot conduct electricity as solids, because there are no mobile charge carriers.
can conduct when molten or dissolved in aqueous solution as there are mobile ions and therefore can carry a charge

Question 18

explain the solubility of ionic compounds in water

Answer 18

soluble in water, ions can form strong attractions to water molecules, sometimes so strong that they can remove ions away from the giant ionic lattice structure and form hydrated ions. Forming ion-dipole bonds (force between an ion and water molecules

Question 19

what is a hydrated ion

Answer 19

ion surrounded by water molecules

Question 20

ion surrounded by water molecules

Answer 20

hydrated ion

Question 21

explain the relationship between graphene and graphite

Answer 21

graphene = one singular layer of carbon atoms
graphite = multiple layers of carbon atoms

Question 22

what properties of graphene mean that it is likely to have important technological applications

Answer 22

very high tensile strength, very good electrical conductor