We might not realise it but metals are an important part of our lives. Ever since the industrial ages, our reliance on metals is very high. We use them for everything, from construction to jewellery. But where do we get these metals from and how is it produced? Let us find out more about the occurrence of a metal.
Occurrence of Metals
The crust of the earth provides metals and it is a good source to procure metals. Mostly, the metals occur in nature in a combined state but sometimes they can also occur in the free state. A native metal is a metal found in its metallic state naturally, either in pure form or in the form of an alloy. Most metals can’t resist natural processes like oxidation, corrosion, etc. Hence, only non-reactive metals like gold, silver, platinum, etc are found in the native or free state. Most metals are obtained in the form of compounds and they need to be filtered from their impurities to be further used for various applications. The process of procuring metals from ores is called metallurgy and these naturally occurring compounds of metals are known as minerals. Metals are usually extracted from the earth by mining.
All ores are minerals, but not all minerals are ores. Ores are those minerals which contain metals. The picture shown above is a gold-bearing ore. Different methods are used to extract different metals. For instance, common metals like iron are smelted using carbon as a reducing agent. Few metals, such as aluminum and sodium, don’t have a commercially practical reducing agent and are extracted using electrolysis instead. Sulfide ores are not reduced directly to the metal but are roasted in air to convert them to oxides.
Gangue or Matrix
The gangue or matrix is an unwanted, commercially useless, rocky, earthy or sandy materials that are found with the ores. These are the impurities are filtered out at a later stage.
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Extraction of Metals
The occurrence of metals in nature is only a part of the process, these metals also have to be extracted. Metallurgy is the process of extracting metals. The basic step of extracting metals is called concentration of ores.
Concentration of Ores
The ores contain a lot of impurities that need to be filtered. The filtration of these impurities from ores is known as concentration. Concentration can be done by gravity separation or hydraulic washings, or froth flotation process.
Metals of high reactivity level
Metals in the top of the reactivity level i.e. metals like sodium, magnesium, calcium, etc cannot be obtained from their compound by heating with carbon as they are very reactive. Electrolytic reduction is used to obtain such metals.
Metals of medium reactivity level
Metals in the middle of the reactivity series i.e metals like lead, zinc, copper, etc are moderately reactive and are generally present as carbonates or sulphides. Sulphides ores are converted into oxides by heating strongly in the presence of excess air. Sulphur impurities can escape as gas, this process is known as roasting. Carbonates ores are calcinated to eliminate carbonate and moisture impurities. Calcination is a process where the ore is converted into oxides by heating strongly in the presence of excess air.
Metals of low reactivity level
Metals that aren’t very reactive are placed low in the reactivity series. These metals can be reduced to metals by heating alone. For example, Mercury is procured from its ore, cinnabar (HgS), by the process of heating. Copper can also be obtained from its sulphide ore (Cu2S) by heating.
Solved Example for You
Q: Which is the most reactive metal?
Ans: The correct answer is option ‘c’. Sodium (Na) is the most reactive metal. Sodium is kept in kerosene so that it doesn’t react with the oxygen and moisture present in the air.