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Chemistry > Metallic bonding > Flashcards

Metallic bonding Flashcards

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1
Q

What are some properties of metals?

A

Thermal conductors
Electrical conductors
High melting point
Malleable- beaten into new shapes
Ductile- drawn into wire
High density- relatively heavy considering the volume
Lustrous
High tensile strength- withstand a lot of stress before failing
Low ionisation energy- easily lose their outer shell electrons

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2
Q

what is high density?

A

relatively heavy considering the volume

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3
Q

what is high tensile strength?

A

withstand a lot of stress before failing

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4
Q

what is low ionisation energy?

A

easily lose their outer shell electrons

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5
Q

how do metals form ions?

A

Lose electrons to achieve a full outer shell.

They form positive ions called cations.

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6
Q

what do transition metals usually look like?

A

silver coloured and are similar in appearance.

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7
Q

what is an important function of transition metals?

A 
Transition metals (ions) are also necessary to assist our bodies in carrying out biochemical reactions such as the production of energy from glucose. 
They are used as paints and glass due to their colours.
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8
Q

what are some properties of transition metals compared to normal metals?

A

Generally harder.
Have higher densities.
Have higher melting points.
May have magnetic properties (iron, nickel and cobalt).
The first three are due to greater core charges making their atoms smaller.

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9
Q

why do transition metals release coloured light?

A

Have partially filled d-sub shells where the d-orbitals are at the same energy level.
When they become part of a compound the d-orbitals no longer have identical energy levels- some are higher.
Electrons are able to become excited between d-orbitals by absorbing energy from white light.
The unabsorbed wavelengths are seen as coloured light.

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10
Q

why is zinc seen as white?

A

Compounds of zinc are seen as white because all of its d-orbitals are occupied therefore they cannot be excited.

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11
Q

why do transition metals have variable valencies?

A

Transition metals may lose electrons from the 3d or 4s sub shells due to their similar energy values.
Sometimes 1, 2 or 3 electrons can be lost with the ions having equal stability.

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12
Q

how is the metallic lattice organised?

A

The positive ions are arranged in a closely packed structure which is regular and 3D.
The valance electrons that are lost are delocalised and are free to move throughout the lattice as they belong to it as a whole.
The electrons remaining in the cations in the inner shells are localised and are not free to move.
This structure is called the metallic bonding model and is described as a lattice of cations surrounded by a sea of delocalised electrons.

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13
Q

what holds the cations and delocalised electrons together?

A

The cations and delocalised electrons are held together by electrostatic forces of attraction which is between the cations and delocalised electrons and is called a metallic bond.

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14
Q

why are metals good conductors of electricity?

A

Delocalised electrons are free to move.
If a source of electric current is attached, electrons flow from positive to negative.
For things to conduct electricity they must have freely moving charged particles.

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15
Q

why are metals good conductors of heat?

A

When delocalised electrons bump into each other and into ions, they transfer energy.
When heated they vibrate more rapidly.

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16
Q

why do metals have high melting and boiling temperatures?

A

High amounts of energy are needed to overcome the strong electrostatic forces of attraction.

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17
Q

why are metals malleable and ductile?

A

Layers of cations can be forced across each other and the delocalised electrons move to compensate for this and re-establish the electrostatic forces.

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18
Q

why are metals usually dense?

A

The ions of the lattice are closely packed.

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19
Q

why are metals lustrous?

A

Delocalised electrons reflect light.

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20
Q

why do metals react by loosing electrons?

A

When delocalised electrons are involved in reactions, the reactivity of the metal depends on how easily the delocalised electrons can be removed.

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21
Q

what are some limitations of the metallic model?

A

Why some metals are magnetic.
Why there is a large range of melting temperatures.
Why there is a large range of densities.
Why there are differences in electrical conductivity.

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22
Q

how reactive are the group 1 metals with water?

A

Group 1 metals are highly reactive with water and need to be stored under oil.

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23
Q

how reactive are group 2 metals with water?

A

Group 2 is quite reactive.

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24
Q

what is produced when metal reacts with water?

A

hydrogen gas

25
Q

how does reactivity change down a group?

A

increases

26
Q

what is the reactivity of transition metals with water?

A

less reactive than groups 1 and 2

27
Q

what is the reactivity of metals with acids?

A

Follows the same pattern as with water.
Metals are usually more reactive with acids.
Some that don’t react with water will with acids.

28
Q

what is group 1’s reactivity with oxygen?

A

Group 1 metals all react to form a metal oxide.

29
Q

what is group 2’s reactivity with oxygen?

A

Group 2 also react but usually require heat.

30
Q

how do transition metals react with oxygen?

A

Transition metals are less reactive but slowly react. Most are mined as oxides and need to be processed to obtain the metal. Gold and platinum are the least reactive and are found in pure form.

31
Q

what metals are most reactive?

A

Metals that require the least amount of energy to remove electrons tend to be the most reactive.

32
Q

how is iron found naturally?

A

Iron is found as an iron oxide combined with rocky material and iron must be extracted before it can be used.
Most iron ore is found in sedimentary rocks in the form of haematite (Fe2O3).
It forms a red colour when exposed to oxygen.

33
Q

what are the raw materials used in iron extraction?

A

Iron ore
Limestone
Coke
Air

34
Q

where is iron ore found?

A

Mined form the ground.

35
Q

how is coke produced? where does this occur?

A

Produced by strongly heating coal in air tight ovens for 15 hours to produce a solid that is 80-90% carbon. where iron extraction occurs.

36
Q

what is limestone made of? how is it prepared for use?

A

Mainly composed of calcium carbonate.

It is mined and crushed before use.

37
Q

what is a blast furnace? where are all the inputs added? how constant is the temperature throughout?

A

It is a tall tower that is heated to high templates and operates continually.
Pre-heated air enters the bottom while the other reactants (charges) are added at the top.
There are different temperature zones where different reactions take place.

38
Q

what happens first in iron extraction?

A

coke reacts with oxygen

39
Q

how does coke react with oxygen? what is created? what are the formula?

A

Air rises and meets the falling charge.
Oxygen reacts with coke.
Carbon + oxygen —> carbon dioxide (complete combustion reaction)
Carbon dioxide + carbon —> carbon monoxide (incomplete combustion)
The first reaction releases a lot of heat help maintain the high temperatures and reaction rate.
No external source of heat is required.

40
Q

what is the second stage of iron extraction?

A

carbon monoxide reacts with iron ore

41
Q

what happens when carbon monoxide reacts with iron ore?

A

A series of reactions occur that finally produce carbon monoxide and iron ore is converted into molten iron metal.
Carbon monoxide + iron oxide —> iron + carbon dioxide

42
Q

what does the limestone do in the reactions?

A

Removes the rocky material that doesn’t melt.
It is broken into calcium oxide which reacts with unwanted material to form slag.
Both iron and slag sink to the bottom but slag is less dense and floats on top.
This prevents the iron from re-oxidising.
The iron and slag are drained out through holes in the bottom and separated.

43
Q

what is iron usually made into?

A

steel on site

44
Q

what is slag used for?

A

road resurfacing and cement.

45
Q

what are environmental issues with iron extraction?

A

loss of landscape, air pollution, slag disposal, noise pollution

46
Q

what are economic issues with iron extraction?

A

financial gain, huge wage differences between mining and non-mining workers

47
Q

what are social issues with iron extraction?

A

indigenous land rights, lang conflicts between mining, farming and tourism, remote mine locations (FIFO workers)

48
Q

why are metals modified?

A

to make them more useful, harder or less expensive.

49
Q

what is alloying? what happens? what are some changed properties?

A

A mixture of elements (either 2 metals or a metal and a non-metal).
This alters their original properties.
They are melted, mixed and allowed to cool.
Alloys are usually harder, less malleable and poorer electrical conductors than pure metals.

50
Q

what is a substitutional alloy?

A

When some of the host metal atoms are replaced with other metal atoms of similar size.
The atoms have similar atomic radii and bonding characteristics.

51
Q

what is interstitial alloying? what are changed properties of the different types? low etc.

A

Formed when some interstices (holes) in the metal structure are filled with small atoms.
One atoms must have a significantly smaller radii.
low - somewhat malleable - bridges, buildings, vehicles
Medium - harder but less ductile - large machinery parts
High - very strong but more brittle - springs
Very high - hard but brittle - cutting tools

52
Q

what are advantages and disadvantages of interstitial alloying?

A

The small atoms make it more difficult for the large ions to slide past each other so the metal is stronger but too much of the smaller atom makes it brittle. Its electrical conductivity can also be reduced because the delocalised electrons are restricted.

53
Q

what are crystals? how many do metals contain? what characteristics of crystals determine properties of metals? what is it called to change the crystals?

A

A crystal is a region in a solid where particles are arranged in a certain way.
Metal will contain a number of crystals.
The areas where the crystals overlap and the size of the crystals determine the way the metal behaves. Rearranging the lattice structure.

54
Q

what is work hardening? what does this change?

A

Beating a metal and rearranging the crustal structure.
The metal is thinner and the grains are more close together.
The metal becomes harder and less brittle.

55
Q

what is annealing? what does it change?

A

Heating a metal to a moderate temperature and cooling slowly.
Large crystals form.
More soft and more ductile.

56
Q

what is quenching? what does it change?

A

Moderate temperature and cooled quickly.
Small crystals.
Harder and more brittle.

57
Q

what is tempering? what does it change?

A

Heating quenched metal again to a lower temperature and cooling.
Crystals of intermediate size.
Metal is hard but less brittle.

58
Q

what are coatings? what do they prevent? how can it be done?

A

Decorative or functional or both.
Surface coating such as tin, paint or powder is used to stop steel reacting with air.
Steel can also be galvanised in zinc. The zinc reacts with oxygen and slows down the corrosion of the iron.

59
Q

what do metallic manomaterials exist as? what can they be used for?

A

particles, rods, wires or tubes. Gold nanoparticles are used in cancer treatment
Silver nanoparticles kill bacteria
Copper nanoparticles used in solder in space crafts
Iron nanoparticles remove pollution in ground water

Chemistry (28 decks)

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