What Are Allotropes of Metalloids and Metals

Learn the basics about allotropes of metalloids and metals, as a part of the overall properties of matter topic. An allotrope is basically a different form of the same element, each with distinct physical and chemical properties. For example, oxygen can exist as diatomic oxygen, or as ozone. Both molecules are made exclusively of oxygen, though their structures and properties are very different from one another. Allotropism can also exist in certain metalloids and metals. Silicon is a very important element – it is used in circuits of many electronic devices, such as your mobile phone and laptop, and in solar cells. Silicon exists in crystalline form, and in non-crystalline form, known as amorphous silicon. In crystalline silicon, silicon atoms are arranged in a tetrahedral structure, with each atom covalently bound to four other atoms. Diamond is an allotrope of carbon. Each carbon atom is covalently bound to four other carbon atoms in the same tetrahedral arrangement. Amorphous silicon is non-crystalline silicon – in this structure, the silicon atoms are not held together tightly like in crystalline silicon. Both crystalline silicon and amorphous silicon can be used to manufacture solar cells, which are grouped together to make solar panels for solar-powered electricity. One day, all cars may run on solar power, and homes cooled or heated with solar panels. Considering that fossil fuel is a non-renewable resource, solar-powered electricity is now at the forefront of innovation and research. Another metalloid with many allotropes is boron – each with its own unique structure. Iron and its alloys are very important in everyday life. Iron is a great example of a metal where allotropism is present. Each allotrope has a different structure, which gives rise to different properties. The interesting concept here is that these different allotropes arise at different temperature and pressures – so one allotrope of iron can change into another allotrope. The three most common allotropes each have a cubic structure. Alpha-iron, beta-iron, and delta-iron have body-centred cubic structures. In this structure, there is an iron atom at the centre of the cube, which is linked to all eight iron atoms at the vertices of the cube. Gamma-iron has a face-centred cubic structure. In this structure, there is an iron atom at each face of the cube. At very high pressures, epsilon-iron is formed, which has a hexagonal close-packed structure. Other metals that exhibit allotropy include lithium, sodium, calcium, and titanium.