Chapter 4 : Metallic Bonding Flashcards Preview

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Flashcards in Chapter 4 : Metallic Bonding Deck (28):
1

Properties of metals

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

2

Metallic bonding

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

3

Why are metals lusterous?

The delocalised electrons in the lattice reflect light

4

Why are metals good conductors of heat?

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

5

Why are metals dense?

The metallic lattices are closely packed

6

Why do metals have high melting and boiling points?

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

7

Why are metals good conductors of electricity?

The delocalised electrons are mobile and therefore an electrical is possible

8

Why are metals malleable and ductile?

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

9

Alloy

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

10

Substitutional ally

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

11

Interstitial alloy

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

12

S block metal properties

Very reactive
Low density
Low melting points

13

D block metal properties

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

14

Limitations of the metallic bonding lattice model

Magnetism
Density
Malleability

15

Ball bearing model

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

16

Ways to modify a metal

Work hardening
Annealing
Quenching
Tempered

17

Work hardened metals

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

18

Annealed metals

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

19

Quenched metals

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

20

Tempered metals

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

21

Surface protection for metals

Plastic
Paint
Grease or oil
Metal coatings

22

Sacrificial coatings

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

23

Noble coatings

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

24

Reaction with oxygen

Alkali metals
Metal + oxygen > metal oxide

25

Reaction with water

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

26

Reaction with acid

Hydrogen is produced
Metal + acid > ionic salt + hydrogen

27

Extraction of metals

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

28

Metallic nanomaterials

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