Air and Molecular Compounds

The earth is surrounded by an atmosphere that is a mixture of gases. Some of these gases are molecular elements, and some are molecular compounds.

The air contains a number of gases. 

air is made up of nitrogen (78%), oxygen (21%) and other gases (1%) (http://www.bbc.co.uk/staticarchive/c0f067f1fda49b3a61d31d9d53b5d11b00c6dd18.gif)

Molecular Compounds;

Most non-metal elements are molecular, and most of these consist of molecules with just 2 atoms joined together. Examples include Nitrogen (N2), Oxygen (O2), Chlorine (Cl2) and Bromine (Br2)

Most compounds between non-metals elements are also molecular. Some examples are Water (H2O), Carbon Dioxide (CO2), Nitrogen Dioxide (NO2) and Ammonia (NH3)

Atoms are joined by Covalent Bonds.

Hydrogen (H2) H - H (http://www.bbc.co.uk/staticarchive/698accbb28339af51a2bf27088ddfa6e99f5078f.gif)two atoms joined with a straight horizontal line (http://www.bbc.co.uk/staticarchive/d271b0874c38bdd5db2cfb79e212c630b3c7bb3a.gif)

Water (H2O)  H - O - H (http://www.bbc.co.uk/staticarchive/fedd20d393f85712b1eda8f22b504fe57dda5aa4.gif)three atoms joined (http://www.bbc.co.uk/staticarchive/543b20df4d369891204cbc6af06cb606396c2c75.gif)

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Ionic Compounds

The earth's hydrosphere is the oceans. They consist mainly of water, with some dissolved compounds. The iconic compounds that are dissolved in sea water are mainly salts and make water taste salty.

Ionic bonding;

When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms, forming ions. The resulting compound is called an Ionic Compound. Ionic Compounds are made up of postive and negative ions. Ionic Compounds have high melting and boiling points because much energy is needed to break down an ionic structure.

E.g, Sodium + Chlorine = Sodium Chloride

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Rocks and Minerals

The earth's lithosphere is the rigid outer layer, which contains many useful chemical compounds.

Crust and Mantle;

The earth's lithosphere is the rigid outer layer that is made up of the crust and the part of the mantle just below it.

The outer-most layer is called the crust. The crust surrounds the mantle, which surrounds the core. There are 2 parts to the core - the outer core and the inner core, which is the inner most part of the Earth's structure. (http://www.bbc.co.uk/staticarchive/18e0518ed5183cd531f908f11031e176c4461b9c.gif)

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Biological Compounds

The biosphere refers to all living organisms, both plants, and animals on earth.

Compounds in living organisms;

living things are mainly made from compounds that contain the elements Carbon, Hydrogen, Oxygen, and Nitrogen. 

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Extraction of Metals

Metals are extracted from ores. An ore is a rock that contains enough of a mineral (metal compound) for the metal to be extracted from it. Most metals are extracted from an ore by reduction with carbon or by electrolysis.

Extraction using carbon;

Metals such as Zinc, Iron and Copper are present in ores as their Oxides. Each of these oxides is heated with carbon to obtain the metal. 


Ionic compounds contain charged particles called ions. Ionic substances can be broken down into the elements they are made from by electricity, in a process called electrolysis.

Extraction of Aluminium;

Aluminum is the most abundant metal on earth. Despite this, it is expensive, largely because of the amount of electricity used up in the extraction process. 

Aluminum ore is called bauxite. The bauxite is purified to yield a white powder, aluminium oxide, from which aluminium can be extracted.

The extraction is done by electrolysis. But first, the aluminium oxide must be made molten so that electricity can pass through it. Aluminium oxide has a very high melting point, so it would be expensive to melt it. Instead, it is dissolved in molten cryolite, an aluminium compound with a lower melting point than aluminium oxide. The use of cryolite reduces some of the energy costs involved in extracting aluminium.

Diagram showing cell for aluminium extraction (http://www.bbc.co.uk/staticarchive/4c219edfdc34f45a785c710ef5cb9cc677b0cc6f.gif)

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Metal Properties

The way that metal atom are arranged to make a crystal lattice gives metals particular properties. The use we make of metals depend on these properties. 

Metal Properties and used;

Most metals are very strong. They have high melting points and they have high heat and electrical conductivity. They are also malleable, which means they can be beaten or pressed into thin sheets.

Metals have their characteristic properties because of their giant structure. In a metal crystal, the atoms are in a regular arrangement and strongly bonded together. Strong metallic bonding makes metals hard but allows layers of atoms to slide so that the metal is malleable. The layers of atoms also allow an electric current to pass through.

The extensive use of metals is having an effect on our environment;

  • ***** mining of metal ores creates large areas of barren and lifeless land
  • Waste material from metal extraction is left in spoil tips that scar the landscape
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