Chapter 4 : Metallic Bonding

Question 1

Properties of metals

Answer 1

Lustrous
Good conductors of heat/electricity
Malleable
Ductile
Dense
High melting/boiling points
Hard
High tensile strength

Question 2

Metallic bonding

Answer 2

When metallic atoms bond to form a lattice, an array of cations surrounded by a sea of delocalised electrons

Question 3

Why are metals lusterous?

Answer 3

The delocalised electrons in the lattice reflect light

Question 4

Why are metals good conductors of heat?

Answer 4

Because the cations and delocalised electrons are mobile and therefore can “bump” together when heated and create more heat

Question 5

Why are metals dense?

Answer 5

The metallic lattices are closely packed

Question 6

Why do metals have high melting and boiling points?

Answer 6

The electrostatic attraction between a cation and delocalised electrons is really strong and increases up by atomic number

Question 7

Why are metals good conductors of electricity?

Answer 7

The delocalised electrons are mobile and therefore an electrical is possible

Question 8

Why are metals malleable and ductile?

Answer 8

The non-directional nature of metallic bonds
Layers of atoms can move past you without disrupting the force between the positive ions and the negative sea of electrons

Question 9

Alloy

Answer 9

Mixing metals with other metals or non-metals to create an alloy which has specific properties, usually to mkae them stronger, flexible and light

Question 10

Substitutional ally

Answer 10

If atoms that are being alloyed are about the same size they can replace the other in the metal crystal

Question 11

Interstitial alloy

Answer 11

If the atoms being alloyed differ greatly in size the smaller atom may fit into the space between larger atoms

Question 12

S block metal properties

Answer 12

Very reactive
Low density
Low melting points

Question 13

D block metal properties

Answer 13

form colourful compounds
Iron, cobalt and nickel are magnetic
Useful catalyts

Question 14

Limitations of the metallic bonding lattice model

Answer 14

Magnetism
Density
Malleability

Question 15

Ball bearing model

Answer 15

Metals with large grains have fewer dislocation and bend easily
Metals with small grains have many dislocations and do not bend easily
A metal with perfect rows of atoms bend easily
If the rows are distorted they cannot slide over one another as easily and therefore do not bend as easily

Question 16

Ways to modify a metal

Answer 16

Work hardening
Annealing
Quenching
Tempered

Question 17

Work hardened metals

Answer 17

Bending or hammering metals create smaller crystal grains and making it stronger and harder to bend
More brittle

Question 18

Annealed metals

Answer 18

Are heated and cooled slowly creating alrge crystal grains that are in perfect rows that bend easily and creating a softer metal
Used to restore ductility

Question 19

Quenched metals

Answer 19

Heated and cooled instantly creating smaller crystals and the grains don’t have time to arrange in perfect rows so creating a harder brittle metal

Question 20

Tempered metals

Answer 20

When quenched metals are heated again and allowed to cool slowly which reduces brittleness and retains hardness

Question 21

Surface protection for metals

Answer 21

Plastic
Paint
Grease or oil
Metal coatings

Question 22

Sacrificial coatings

Answer 22

Using a more reactive metal so that the coating will react with the environment not the metal
Galvanising

Question 23

Noble coatings

Answer 23

Less reactive metal to cover the metal and that won’t be scratched or broken as breaking the coating will result in quick corrosion of the metal underneath
Used because they are usually harmless whereas more reactive tend to be harmful to people

Question 24

Reaction with oxygen

Answer 24

Alkali metals

Metal + oxygen > metal oxide

Question 25

Reaction with water

Answer 25

Alkali metals
Produce alkalis and hydrogen gas
Group 1 metal + water > group 1 metal hydroxide + hydrogen

Question 26

Reaction with acid

Answer 26

Hydrogen is produced

Metal + acid > ionic salt + hydrogen

Question 27

Extraction of metals

Answer 27

Depends on reactivity
Unreactive are found in their natural state
Less reactive you heat the metal ore in the air
Reactive you heat the metal ore with carbon
More reactive you use electrolysis of molten compound, using electricity to cause a chemical reaction

Question 28

Metallic nanomaterials

Answer 28

The high surface area to volume ratio increases reactivity and catalytic potential
Have different physical and chemical properties but have the same metallic structure