5.01 : Metals in the earths crust The composition of the Earth’s crust we get some metals from the sea but most from earths crust.The Crust is the outer llayer of the Earth. It is huge mixture of many different compunds. It also contains elements such as sulphur,copper,silver,platinum and gold. These occur uncombined, or native, because they are unreactive. if you could dig up the earths crust and break down all the comnpunds, you would find it is almost half oxygen! its composition is oxygen 45% ( nearly one-fourth ) silicon 27% ( over one foruth) all other metals and non-metals 2% pottasium 1.5% sodium 2.5% magnesium 3% calcium 5% iron 6% aluminium 8% Nearly three-quarters of the earth’s crust is made up of just two non-metals, oxygen and silicon. These are found combined in compunds such as aluminium oxide,iron oxide,and calcium carbonate. the rest of the crust consists mainly of just six metals.Aluminium is the most abundant of these, and iron is next.None of the six is found uncombined, because they all are reactive metals,and reactice metals like to form compounds. Some metals are scarce : look again at the pie chart above. it shows that there are just 6 plentiful metals. all the other metals together make up less than one-fifth of the earths crust,so they are not plentiful. copper zinc mercury silver lead gold tin platinum the scarce metals are expensive. Even so, we are using them up quicly, and many people are worried that they will soon run out. Metal ores: The rocks in the Earths’s crust are a mixture of many different compounds. But some contain a large amount of single metal compound ,or a single metal,and it may be worth digging up these extracted metals.Rocks which metals are obtained are called ores.Below are some examples: Mine or not to mine? Before starting to mine an ore,the mining company must decide whether it is economical.It must find questions like these: 1.How much ore is there? 2.How much metal will we get from it? 3.Are there any special problems about getting the ore out? 4.How much will it cost? 5.how much will be able to sell the metal for? 6.so will me make a profit if we go ahead? the answers to these questions will change from year to year.if the costs of fuel drops,and the selling price of a metal rises,even a low quality or low-grade ore may be worth mining. The mining company must also think about local community,who may worry that the landscape will be ruined by dust,pits,scars, and that the extraction plant will cause pollution.on the other hand,they may welcome the new jobs tthe mining will bring.

Ox45%ygen

Oxygen 45%

Silicon 27%

Silicon 27%

All the other metals and non metals 2%

metals and non metals 2%

p

Pottasium 1.5%

sodium 2.5%

sodium 2.5%

others

magnesium-3%
calcium-5%
iron-6%
Aluminium-8%