CHEMICALS OF THE NATURAL ENVIRONMENT C5 21 ST CENTURY SCIENCE

Lesson 1: Covalent Bonding WALT Describe how atoms can share electrons in a covalent bond WILF You being able to draw diagrams to show how atoms in simple molecules (oxygen, water, methane) are held together

WALT

Describe how atoms can share electrons in a covalent bond

WILF

You being able to draw diagrams to show how atoms in simple molecules (oxygen, water, methane) are held together

Attractive forces between molecules are weak. Small molecules are gases or liquids at room temperature.

Attractive forces between molecules are weak.

Small molecules are gases or liquids at room temperature.

The bonds inside molecules are strong. Water molecules do not fall apart when the liquid boils and turns to steam. water molecule water molecule

The bonds inside molecules are strong.

Water molecules do not fall apart when the liquid boils and turns to steam.

Electron Configurations What is the electron configuration of the following (atomic number in brackets): Hydrogen (1) Lithium (3) Carbon (6) Nitrogen (7) Aluminium Atomic number = number of protons = number of electrons

What is the electron configuration of the following (atomic number in brackets):

Hydrogen (1)

Lithium (3)

Carbon (6)

Nitrogen (7)

Aluminium

How are the atoms in an H 2 molecule held together? To picture this you need to look at the structure of a hydrogen atom. The positively charged nucleus and the negatively charged electron attract each other.

How are the atoms in an H 2 molecule held together?

To picture this you need to look at the structure of a hydrogen atom.

The positively charged nucleus and the negatively charged electron attract each other.

When two hydrogen atoms approach each other . . . . . . the electron of one atom and the nucleus of the other atom start to attract each other.

When two hydrogen atoms approach each other . . .

. . . the electron of one atom and the nucleus of the other atom start to attract each other.

When the atoms are close, the attractions are so strong that a molecule of hydrogen (H 2 ) is formed. The atoms are held together by the attractions between the two nuclei and the shared pair of electrons. This is a single covalent bond.

When the atoms are close, the attractions are so strong that a molecule of hydrogen (H 2 ) is formed.

The atoms are held together by the attractions between the two nuclei and the shared pair of electrons. This is a single covalent bond.

Chemists draw a line between element symbols to show a covalent bond. H—H hydrogen, H 2 O O oxygen, O 2 N N nitrogen, N 2 O C O carbon dioxide, CO 2 H H—C—H H methane, CH 4 H H H—C—C—O—H H H ethanol, C 2 H 5 OH O H H water, H 2 O

Covalent bonding in chlorine Chlorine (2.8.7) needs 1 more electron to have a completely full outer shell. To achieve this, it can share an electron with another chlorine atom. This creates a single bond. Cl Cl Cl 2 or Cl–Cl Cl

Covalent bonding in oxygen Oxygen (2.8.6) needs 2 more electrons to have a completely full outer shell. To achieve this, it can share two electrons with another oxygen atom. This creates a double bond . O O 2 or O=O O O O

Covalent bonding in nitrogen Nitrogen (2.8.5) needs 3 more electrons to have a completely full outer shell. It can share three electrons with another nitrogen atom to do this. This creates a triple bond . N 2 or N ≡N N N N N

Covalent bonding in methane How are carbon and hydrogen bonded in methane? 2.4 1 4 1 1 4 Ratio of atoms Electrons needed Electron configuration H C CH 4 or H C H H H C H H H H

Chemists have different ways of describing molecules. molecular formula displayed formula with lines for covalent bonds ball-and-stick model space-filling model

Lesson 2: The Earth’s Spheres WALT Recall that the Earth is made up of 4 different spheres WILF You being able to describe the 4 spheres: atmosphere, hydrosphere, lithosphere, and biosphere

WALT

Recall that the Earth is made up of 4 different spheres

WILF

You being able to describe the 4 spheres: atmosphere, hydrosphere, lithosphere, and biosphere

The Structure of the Earth The average density of the Earth is much higher than the crust, so the inner core must be very dense A thin crust - 10-100km thick A mantle – has the properties of a solid but it can also flow A core – made of molten nickel and iron. Outer part is liquid and inner part is solid

What do you know about the Earth? Put the following list of Earth facts in order of size, starting with the largest thing first! Don’t panic: you only need to guess.

Put the following list of Earth facts in order of size, starting with the largest thing first!

Don’t panic: you only need to guess.

Put these Earth facts in order of size A The height of the tallest MOUNTAIN B The depth of the Earth’s ATMOSPHERE C The depth of the deepest OCEAN D The depth of the Earth’s CRUST E The depth of the deepest LAKE

Were you right? B The depth of the Earth’s ATMOSPHERE D The depth of the Earth’s CRUST C The depth of the deepest OCEAN A The height of the tallest MOUNTAIN E The depth of the deepest LAKE

The Earth is the source of all our materials. We can get things from: the atmosphere the lithosphere the biosphere the hydrosphere Chemicals from the Earth’s spheres

The Earth is the source of all our materials.

We can get things from:

the atmosphere

the lithosphere

the biosphere

the hydrosphere

Definitions The atmosphere The lithosphere The hydrosphere The biosphere Mixture of gases that surround the Earth. It includes oxygen we need to survive and water vapour. 78% N 2 , 20% O 2 , 1% Ar. Solid crust and top part of mantle, contains rocks and mantle we use for raw materials. All the water on the surface of the Earth (oceans, seas, rivers and lakes) and the chemicals dissolved in them. Includes all living things including plants and animals

The atmosphere

The lithosphere

The hydrosphere

The biosphere

Mixture of gases that surround the Earth. It includes oxygen we need to survive and water vapour. 78% N 2 , 20% O 2 , 1% Ar.

Solid crust and top part of mantle, contains rocks and mantle we use for raw materials.

All the water on the surface of the Earth (oceans, seas, rivers and lakes) and the chemicals dissolved in them.

Includes all living things including plants and animals

Use the data table to fill in the table

Where on Earth For each character use the speech bubble to describe some physical properties of materials which are found there. Think about the physical state of the materials, their melting points (high or low) and their solubility.

For each character use the speech bubble to describe some physical properties of materials which are found there. Think about the physical state of the materials, their melting points (high or low) and their solubility.

Lesson 3: The Atmosphere WALT Understand that humans can affect the balance of chemicals in the atmosphere; relate relative formula mass to chemical properties WILF You being able to tell me how mass affects the boiling points of chemicals

WALT

Understand that humans can affect the balance of chemicals in the atmosphere; relate relative formula mass to chemical properties

WILF

You being able to tell me how mass affects the boiling points of chemicals

N 2 is a very unreactive gas. It makes up 78% of the air. O 2 makes up 21% of the air. Ar is one of the noble gases. It is very unreactive. It makes up 1% of the air. CO 2 makes up only 0.03% of the air. H 2 O is present in moist air. Water cycles between the four spheres. All living things remove O 2 from the air by respiration. O 2 is given out by green plants in sunlight. It is a product of photosynthesis. CO 2 is given out by all living things during respiration. CO 2 is taken in by plants during photosynthesis. Nitrogen is not completely inert. During thunderstorms some N 2 reacts with O 2 . The products are washed out of the air by rain. This can add nitrates to soil. Volcanoes are a natural source of gases which cause pollution.

What happens to air pollutants? CO 2 is absorbed by plants. Particulate carbon is deposited on surfaces, making them dirty. Ozone, O 3 , is a secondary pollutant produced in the lower atmosphere. SO 2 and NO 2 react with water vapour in the atmosphere to make ‘acid rain’. CO is very poisonous and remains unchanged for some time. NO turns rapidly to the secondary pollutant NO 2 . CO 2 dissolves in the oceans.

Lesson 4: The Hydrosphere WALT Describe how to separate ionic solids from water WILF You being able to carry out an effective evaporation practical

WALT

Describe how to separate ionic solids from water

WILF

You being able to carry out an effective evaporation practical

Sun evaporation condensation rain rivers weathering of rocks followed by dissolving of soluble salts solutions of soluble salts and sediment end up in the sea

Formation of sodium chloride 1. Formation of sodium ions Sodium has 1 electron in its outer shell. If it loses this it will have no partially filled shells. Sodium 1+ ion (2.8.0) Sodium atom (2.8.1) This only happens if there is another atom able to accommodate the lost electron. Loses 1 electron Na Na+

Sodium has 1 electron in its outer shell.

Formation of sodium chloride 2.Formation of Chloride ions Chlorine has 7 electrons in its outer shell. If it gains 1 electron it can achieve a full outer electron shell. It is, therefore, going to be able to accept the electron that the sodium wants to lose. Chlorine atom (2.8.7) Chlorine I - ion (2.8.8) Gains 1 electron (from sodium) Cl Cl

Chlorine has 7 electrons in its outer shell.

Water is a liquid at room temperature. Water is a good solvent even for salts.

Water is a liquid at room temperature.

Water is a good solvent even for salts.

+ When NaCl is added to water, the ions are pulled off the structure and they become free to move in the water. The ions can move independently, so a solution of NaCl in water conducts electricity.

When NaCl is added to water, the ions are pulled off the structure and they become free to move in the water.

The ions can move independently, so a solution of NaCl in water conducts electricity.

Salt harvesters in Thailand raking salt into piles

Machinery at work inside a salt mine

The Earth’s Structure Beneath the atmosphere the Earth consists of 4 main layers:

Lesson 5: The Lithosphere and Biosphere WALT To describe some of the chemicals that are found in the lithosphere and biosphere WILF You being able to tell me 3 properties of silicon dioxide and being able to name 3 types of biological compound

WALT

To describe some of the chemicals that are found in the lithosphere and biosphere

WILF

You being able to tell me 3 properties of silicon dioxide and being able to name 3 types of biological compound

+ When NaCl is added to water, the ions are pulled off the structure and they become free to move in the water. The ions can move independently, so a solution of NaCl in water conducts electricity.

When NaCl is added to water, the ions are pulled off the structure and they become free to move in the water.

The ions can move independently, so a solution of NaCl in water conducts electricity.

Just in at number 10 , forming 0.1% is . . . . . . phosphorus . This non-metallic element is found mainly as the mineral phosphate.

Just in at number 10 , forming 0.1% is . . .

. . . phosphorus .

This non-metallic element is found mainly as the mineral phosphate.

At number 9 with 0.5% is . . . . . . titanium . This useful metal is commonly found as the oxides rutile and ilmenite.

At number 9 with 0.5% is . . .

. . . titanium .

This useful metal is commonly found as the oxides rutile and ilmenite.

Almost 1.5% higher, at number 8 with 2.5% is . . . . . . magnesium . Another metallic element, this is found in minerals such as magnesite and dolomite.

Almost 1.5% higher, at number 8 with 2.5% is . . .

. . . magnesium .

Another metallic element, this is found in minerals such as magnesite and dolomite.

Just above magnesium at number 7 is . . . . . . potassium , with 2.6%. This metallic element is found extensively in potash and sylvite.

Just above magnesium at number 7 is . . .

. . . potassium , with 2.6%.

This metallic element is found extensively in potash and sylvite.

Coming in at number 6 with 2.8% is a close relative of potassium – it’s . . . . . . sodium . This is found in a number of minerals but particularly in rock salt or halite.

Coming in at number 6 with 2.8% is a close relative of potassium – it’s . . .

. . . sodium .

This is found in a number of minerals but particularly in rock salt or halite.

Moving up to number 5 with 3.6% is yet another metal . . . . . . calcium . This element is found in limestone and gypsum.

Moving up to number 5 with 3.6% is yet another metal . . .

. . . calcium .

This element is found in limestone and gypsum.

At number 4 with 5% is . . . . . . iron . The most common ore of iron is haematite (iron oxide).

At number 4 with 5% is . . .

. . . iron .

The most common ore of iron is haematite (iron oxide).

Moving in to the top three, at number 3 we have the final metallic element . . . . . . aluminium , with 8.1%. It’s found mainly as the oxide bauxite.

Moving in to the top three, at number 3 we have the final metallic element . . .

. . . aluminium , with 8.1%.

It’s found mainly as the oxide bauxite.

At number 2 is a non-metal . . . . . . silicon , with a mighty 27.7%. Silicon is found as the oxide in quartz, sand, and amethyst, and as silicate minerals such as clay and feldspar.

At number 2 is a non-metal . . .

. . . silicon , with a mighty 27.7%.

Silicon is found as the oxide in quartz, sand, and amethyst, and as silicate minerals such as clay and feldspar.

Finally, in the number 1 spot with an enormous 46.6% is . . . . . . oxygen . Oxygen is a non-metallic gas found in a wide variety of oxide minerals.

Finally, in the number 1 spot with an enormous 46.6% is . . .

. . . oxygen .

Oxygen is a non-metallic gas found in a wide variety of oxide minerals.

The 10 most abundant elements in the continental crust. O Si Al Fe Ca Na K Mg Ti P percentage relative abundance 50 40 30 20 10

Silica shares some properties of both giant ionic and simple covalent structures. metal and non-metal not soluble in water hard crystalline solid low m.p. electrical conductor in solution or molten high m.p. non-metals Silicon Dioxide properties of silicon dioxide properties of substances with giant ionic structures properties of substances with simple covalent molecules

Each silicon atom can make four bonds and each oxygen atom can make two.

An oxygen atom can act as a bridge between two silicon atoms.

This leaves each silicon able to link with three more oxygen atoms.

This in turn allows the oxygen atoms to act as bridges to more silicon atoms and so on. Eventually a giant covalent structure is formed with millions of silicon and oxygen atoms.

This in turn allows the oxygen atoms to act as bridges to more silicon atoms and so on.

Eventually a giant covalent structure is formed with millions of silicon and oxygen atoms.

The many strong covalent bonds in this giant structure make silica a very hard, high melting point solid. This makes it useful for manufacturing materials such as sandpaper and abrasives.

The many strong covalent bonds in this giant structure make silica a very hard, high melting point solid.

This makes it useful for manufacturing materials such as sandpaper and abrasives.

Other giant covalent structures include diamond and graphite.

The biosphere exists in a thin zone of air, soil, and water that is able to support life. It reaches from about 10 km into the atmosphere down to the bottom of the deepest oceans. hydrosphere biosphere lithosphere atmosphere lithosphere biosphere

The biosphere exists in a thin zone of air, soil, and water that is able to support life.

It reaches from about 10 km into the atmosphere down to the bottom of the deepest oceans.

Living things are made up of only around 25 elements of which approximately 99% are C, H, N, and O.

A small proportion of these elements are present as ionic compounds such as sodium chloride, which is dissolved in our urine and in our blood plasma . . .

. . . and calcium phosphate, which forms part of our bone structure.

vitamin A However, most of the C, H, N, and O is present in the form of large covalent molecules built mainly around chains of carbon atoms.

Enzymes are proteins. The enzyme lysozyme catalyses the breakdown of cell walls of bacteria and helps to protect us from infection.

The angles between the bonds that hold the atoms together in DNA result in its double helix shape.

Lesson 7: Extraction of Metals WALT: Explain that ores are rocks that contain minerals that can be extracted WILF You extracting a metal and writing an equation for it By the end of the lesson you should:

WALT:

Explain that ores are rocks that contain minerals that can be extracted

WILF

You extracting a metal and writing an equation for it

Getting metals from ores First substances other than the metal compound are removed (concentration). Next the metal itself is extracted from its compound (reduction). Most metals do not occur naturally (native). They have to be extracted from metal containing rocks (ores).

First substances other than the metal compound are removed (concentration).

Next the metal itself is extracted from its compound (reduction).

Extraction of metals and energy changes The more vigorously an element forms compounds the harder it will be to get back that element from its compounds. For example, magnesium gives out lots of heat when it combines with oxygen. This means we will have to put lots of energy back to extract magnesium from magnesium oxide and so it will be hard to extract.

The more vigorously an element forms compounds the harder it will be to get back that element from its compounds.

For example, magnesium gives out lots of heat when it combines with oxygen.

This means we will have to put lots of energy back to extract magnesium from magnesium oxide and so it will be hard to extract.

Extracting Gold Because gold occurs native its extraction is a low-tech affair that simply involves finding it!

Because gold occurs native its extraction is a low-tech affair that simply involves finding it!

Iron is a moderately reactive metal. Iron ore is plentiful and relatively easily reduced to iron metal by heating with coal (carbon). It is therefore cheap. It is strong and malleable (non-brittle). Iron is the most commonly used metal.

Iron is a moderately reactive metal.

Iron ore is plentiful and relatively easily reduced to iron metal by heating with coal (carbon). It is therefore cheap.

It is strong and malleable (non-brittle).

Iron is the most commonly used metal.

OILRIG Oxidation Is Loss Reduction Is Gain E.g. Fe +3 + 3e - Fe Cu +2 + 2e - Cu

Oxidation Is Loss

Reduction Is Gain

E.g. Fe +3 + 3e - Fe

Cu +2 + 2e - Cu

Reactions - Reduction of iron ore carbon + oxygen  carbon dioxide Carbon dioxide + carbon  carbon monoxide Carbon monoxide + iron oxide  iron + carbon dioxide C(s) + O 2 (g)  CO 2 (g) CO 2 (g) + C(s)  2CO(g) 3CO(g) + Fe 2 O 3 (s)  2Fe(s) + 3CO 2 (g)

Extracting iron – The Blast Furnace

Lesson 7: How much Metal? WALT Write equations for the reduction of metals and calculating masses of reactants and products WILF You being able to write balanced symbol equations for extraction of metals

WALT

Write equations for the reduction of metals and calculating masses of reactants and products

WILF

You being able to write balanced symbol equations for extraction of metals

State Symbols These tell you whether a material is a solid, liquid or gas when you write a symbol equation: Solid: (s) Liquid: (l) Gas: (g) A solution is denoted using the symbol (aq) which is shorthand for “aqueous”.

These tell you whether a material is a solid, liquid or gas when you write a symbol equation:

Solid: (s)

Liquid: (l)

Gas: (g)

A solution is denoted using the symbol (aq) which is shorthand for “aqueous”.

Lesson 8: Electrolysis WALT Describe how a metal can be purified by applying an electrical current in electrolysis WILF Higher: You being able to write down equations to explain what happens to ions during electrolysis Foundation: You knowing how to carry out an electrolysis reaction and making sure all safety precautions are followed

WALT

Describe how a metal can be purified by applying an electrical current in electrolysis

WILF

Higher: You being able to write down equations to explain what happens to ions during electrolysis

Foundation: You knowing how to carry out an electrolysis reaction and making sure all safety precautions are followed

Copper purification: The whole process

Copper ions form at the anode Impure copper is used as the anode of an electrolysis cell. The battery pulls electrons off the copper atoms in the anode. By losing electrons these atoms become copper ions and so the anode slowly ‘dissolves’ away. Impurities just sink to the bottom as ‘anode mud’.

Impure copper is used

as the anode of an electrolysis cell.

The battery pulls electrons off the copper atoms in the anode.

By losing electrons these atoms become copper ions and so the anode slowly ‘dissolves’ away.

Impurities just sink to the bottom as ‘anode mud’.

Copper atoms at the cathode Opposite charges attract. Positive copper ions ( Cu 2+ ) move towards the negative cathode. At the cathode these ions gain electrons and turn into copper atoms. So, during electrolysis a copper cathode gets thicker.

Opposite charges attract.

Positive copper ions ( Cu 2+ ) move towards the negative cathode.

At the cathode these ions gain electrons and turn into copper atoms.

So, during electrolysis a copper cathode gets thicker.

Purification: The half reactions Anode (+ve electrode) Cu(s)  Cu 2+ (aq) + 2e - Cathode (-ve electrode) Cu 2+ (aq) + 2e -  Cu(s)

Lesson 9(F): Life Cycle of Metals WALT You being able to describe the metallic bonding and use this to explain why metals are so useful WILF For a specific metal, you being able to state how we use it and why it is useful

WALT

You being able to describe the metallic bonding and use this to explain why metals are so useful

WILF

For a specific metal, you being able to state how we use it and why it is useful

In a metal crystal the atoms are packed as close together as possible. This is a giant structure.

In a metal crystal the atoms are packed as close together as possible.

This is a giant structure.

Metallic bonding is strong bonding. Each metal atom contributes one or two electrons to a shared ‘sea’ of electrons. The shared bonding electrons can move through the whole metal structure.

Metallic bonding is strong bonding.

Each metal atom contributes one or two electrons to a shared ‘sea’ of electrons.

The shared bonding electrons can move through the whole metal structure.

2 Iron is the most abundant metal in the lithosphere. 3 All the really valuable ores come from underground mining. Metal ores – true or false? 1 All metals are found in the Earth as compounds.

A vein of gold in quartz rock

The mineral ore haematite (iron oxide) is mined as the principal source of the metallic element iron.

A disused tin mine in Cornwall

A crane filling railroad cars in an open cast copper mine

1 The removal of oxygen from a metal compound is called reduction. 2 Carbon is oxidized in a blast furnace. 3 Aluminium oxide conducts electricity when solid and when liquid. Metal extraction – true or false?

A blast furnace runs continuously, making hundreds of thousands of tons of iron per year.

carbon anodes solid crust of electrolyte insulation molten aluminium oxide molten aluminium tapping hole carbon lining of cell (cathode) + - Making aluminium by electrolysis

2 All metals conduct electricity when solid and when liquid. 3 All metals corrode in moist air. Metal properties and uses – true or false? 1 All metals are strong in tension.

Which properties of metals does this illustrate?

Which properties of metals does this illustrate?

2 The bonding between metal atoms is strong. 3 An electric current in a metal is a flow of electrons. Metal structure and bonding – true or false? 1 Metals are made up of molecules.

2 Recycling rates are higher for metals than most other materials. 3 Recycled steel is not as strong as new steel. Metal waste and recycling – true or false? 1 Iron is the only metal that can be recycled economically.

What are the economic and environmental benefits of recycling iron?

What are the economic and environmental benefits of recycling aluminium?

Copper is purified to improve its NOT CIVIC DUTY Copper is purified by CELERY IS LOST Pure copper forms at the DO TEACH Impurities form called A ODD MENU The anode will slowly DIVE LOSS At the cathode copper ions gain CORN STEEL conductivity electrolysis cathode anode mud dissolve electrons Unscramble the words to end the sentences

Copper is purified to improve its

NOT CIVIC DUTY

Copper is purified by

CELERY IS LOST

Pure copper forms at the

DO TEACH

Impurities form called

A ODD MENU

The anode will slowly

DIVE LOSS

At the cathode copper ions gain

CORN STEEL

Lesson 9 (H): Extraction of Aluminium by Electrolysis WALT Describe and illustrate the extraction of aluminium WILF You being able to write down equations to show the electrode reactions

WALT

Describe and illustrate the extraction of aluminium

WILF

You being able to write down equations to show the electrode reactions

Aluminium: ores It occurs as bauxite ore which is a form of aluminium oxide. Because aluminium is so reactive carbon is unable to pull away the oxygen from it. It is extracted by electrolysis of molten bauxite. Early attempts at this failed because bauxite is so hard to melt. If cryolite is added, the bauxite melts more easily. This is an essential step in the extraction process.

It occurs as bauxite ore which is a form of aluminium oxide.

Because aluminium is so reactive carbon is unable to pull away the oxygen from it.

It is extracted by electrolysis of molten bauxite. Early attempts at this failed because bauxite is so hard to melt.

If cryolite is added, the bauxite melts more easily. This is an essential step in the extraction process.

A bauxite / cryolite mixture is melted in a steel container containing a carbon lining. Tank lined with carbon cathode Steel case Graphite anodes are inserted into the molten electrolyte ready for electrolysis. Electrolytic extraction don't have to copy Graphite (carbon) anodes Molten electrolyte bauxite + cryolite

Opposite charges attract. And so positive aluminium ions move towards the negative cathode. At the cathode these ions gain electrons and turn into aluminium atoms. At the Cathode (Metal Formation):

Opposite charges attract.

And so positive aluminium ions move towards the negative cathode.

At the cathode these ions gain electrons and turn into aluminium atoms.

Negatively charged oxide ions move to the anode (carbon blocks). Here they lose 2 electrons and so turn into neutral oxygen atoms. These atoms rapidly join into pairs to form oxygen gas. At the Anode: Oxygen Formation

Negatively charged oxide ions move to the anode (carbon blocks).

Here they lose 2 electrons and so turn into neutral oxygen atoms.

These atoms rapidly join into pairs to form oxygen gas.

Carbon dioxide formation Remember the electrolysis is carried out at high temperature. Under these conditions quite a lot of the oxygen reacts with the carbon anode. Carbon dioxide is formed and the anode is rapidly eaten away and frequently has to be replaced.

Remember the electrolysis is carried out at high temperature.

Under these conditions quite a lot of the oxygen reacts with the carbon anode.

Carbon dioxide is formed and the anode is rapidly eaten away and frequently has to be replaced.

Extraction of aluminium: overall siphon Graphite / carbon anodes Molten aluminium Molten electrolyte bauxite + cryolite Tank lined with carbon cathode Molten aluminium out Steel case Vented cover

In a metal crystal the atoms are packed as close together as possible. This is a giant structure.

In a metal crystal the atoms are packed as close together as possible.

This is a giant structure.

Metallic bonding is strong bonding. Each metal atom contributes one or two electrons to a shared ‘sea’ of electrons. The shared bonding electrons can move through the whole metal structure.

Metallic bonding is strong bonding.

Each metal atom contributes one or two electrons to a shared ‘sea’ of electrons.

The shared bonding electrons can move through the whole metal structure.