Occurrence of Metals

How do metals occur in nature?

Our earth’s topmost layer which is also known as crust is the main source of metals. Some metals which form soluble salts are found in sea water in the form of their soluble salts.

• The elements or compounds that occur naturally in the earth’s crust are known as minerals.
• These minerals contain high percentage of a particular metal and the metal can be profitable extracted from it.
• The minerals from which metals can be extracted are called ores.
• The most abundant metal on the earth’s crust is aluminium. Whose percentage is about 7%. And the remaining metals are present in very small amount.

Extraction of Metals

According to the activity series the metals are dived into three parts:

1. Metals of low reactivity

• It consists of gold, silver, platinum and copper which are found in free state.
• Copper and silver are also found in combined state as their sulphide or oxide.

2. Metals of middle reactivity

• It consists of metals like Zn, Fe, Pb etc which are moderately reactive.
• They are mainly found in earth’s crust as oxides, sulphides or carbonates. 

3. Metals of high reactivity

• It consists of metals like K, Na, Ca, Mg etc which lie on the top of the activity series and are never found in free state. They are always found in combined state.

What is Metallurgy?

• The various steps involved in the extraction of metals from their ores followed by refining of the metal is called metallurgy.

The various steps that are involved in extraction of metals from their ores are:

Extracting of metals which lie low in the activity series

• The metals that lie low in the activity series are very unreactive. The oxides of these metals can be reduced to metals by heating them alone. 
• For example, cinnabar (HgS) is an ore of mercury. When it is heated in air. It is first converted into mercury oxide and reduced to mercury on further heating.

2HgS (s) + 3O₂ --^heat---> 2HgO (s) + 2SO₂ (g)

2HgO (s) + O₂ --^heat---> 2Hg (l) + 2O₂ (g)