Metals and their Properties
Metals are generally solid materials which are typically shiny, lustrous, ductile and a good conductor of electricity. Example: Aluminium (Al), Iron (Fe), Gold (Au).
Properties of Metals
Metals are good conductors of electricity
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In the structure of metals many atoms are arranged in layered forms. The electron of the higher energy shells of each atoms requires to be full in order to be in a balanced state. However, if the higher energy shells are not full ( example : lithium which has only 2 electron in the second shell and required number is 8) it delocalises. The delocalised electrons leave the atoms and form an electron sea which carry heat and electricity. So in metals, we have a series of positive ions with delocalised electrons holding the ions together by electrostatic attractions which is called : METALLIC BONDING.
Metals can be bent and hammered into different shapes.
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The atoms in a metal are arranged in layers so they can easily slide over each other and give metal the desired shape. On the other hand, alloys are mixture of two metals. When they enter the structure there are two different sizes of atoms present in the same structure . As a result, they become hard and it becomes difficult to slide the Atomic layer and give them the desired shape. The pure metals like gold, are very soft and it is difficult to make jewellery out of it as it can get damaged easily. So they are mixed with other metals and made alloy to make them harder.
Example : Gold alloys
Note: There is a specific type of alloy called shape memory alloys. They have a tendency to return back to their original shape even if the shape has been changed.
Example : Nitinol
They are used in dental braces to shape the teeth. They are stretched to form braces and fitted in the denture. After some time it returns back to its original shape giving the teeth its shape.
We have already studied above that in a metal the atoms are arranged in layers. All of them have free electrons in their outer shells and tend to be delocalised as the higher energy shells are not full . These delocalised electrons form an electron sea and are attracted by strong electrostatic forces to positive atom ions. This electrostatic force of attraction that keep the metal intact in its shape, is called metallic bonding.Example : Iron (Fe)
|Iron (Fe) Atomic Structure|
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