Allotropes of carbon
Diamond, graphite and fullerenes (substances that include A long cylindrical molecule made from carbon atoms joined together by covalent bonds. and A molecule comprising carbon atoms joined together to form a spherical or nearly spherical hollow structure., such as buckminsterfullerene) are three A different form of the same element in the same state. For example, diamond and graphite are allotropes of carbon. of pure carbon.
In all three allotropes, the carbon All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. are joined by strong A bond between atoms formed when atoms share electrons to achieve a full outer shell of electrons., but in such different arrangements that the properties of the allotropes are very different.
Diamond
A diamond is one giant A collection of two or more atoms held together by chemical bonds. of carbon atoms. Diamonds are colourless and Able to be seen through.. They sparkle and reflect light, which is why they are described as Shiny and reflective.. These properties make them desirable in items of jewellery.
Diamond is extremely hard and has a high melting point. For this reason, it is very useful in cutting tools. The cutting edges of discs used to cut bricks and concrete are tipped with diamonds. Heavy-duty drill bits 鈥 such as those used in the oil exploration industry to drill through rocks 鈥 are made with diamonds so that they stay sharp for longer.
Diamond is Unable to dissolve in a particular solvent. For example, sand is insoluble in water. in water. It does not To allow electricity, heat or other energy forms to pass through. electricity. Every atom in a diamond is bonded to its neighbours by four strong covalent bonds, leaving no free Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. and no Electrically charged particle, formed when an atom or molecule gains or loses an electron/electrons.. This explains why diamond does not conduct electricity.
The bonding also explains the hardness of diamond and its high melting point. Significant quantities of energy would be needed to separate atoms so strongly bonded together.
Graphite
Graphite contains layers of carbon atoms.
Graphite is black, shiny and Not transparent or see-through.. It is not transparent. It is also a very slippery material. It is used in pencil leads because layers easily slide onto the paper, leaving a black mark. It is a component of many lubricants, for example bicycle chain oil.
Graphite is insoluble in water. It has a high melting point and is a good conductor of electricity, which makes it a suitable material for the A conductor used to establish electrical contact with a circuit. The electrode attached to the negative terminal of a battery is called a negative electrode, or cathode. The electrode attached to the positive terminal of a battery is the positive electrode, or anode. needed in The decomposition (breakdown) of a compound using an electric current..
Each carbon atom is bonded into its layer with three strong covalent bonds. This leaves each atom with a spare electron, which together form a delocalised 鈥榮ea鈥 of electrons loosely bonding the layers together. These delocalised electrons can all move along together 鈥 making graphite a good electrical conductor.
However, melting graphite is not easy. It takes considerable energy to break the strong covalent bonds and separate the carbon atoms.
Nanotubes
Nanotubes are a type of fullerene and are molecular-scale tubes of carbon arranged similarly to the layers in graphite.
Carbon nanotubes have a very high melting point, as each carbon atom is joined to three other carbon atoms by strong covalent bonds. This also leaves each carbon atom with a spare electron, which forms a sea of delocalised electrons within the tube, meaning nanotubes can conduct electricity.