Carbon Bonding

Goal of the class Discuss the different structural elements of carbon bonding Question of the day: What are the allotropes of carbon? Previous Answer: Lewis dot structures show the atom and the number of valence electrons. Previous question: What do Lewis dot structures show?

Carbon Bonding Carbon’s four valence electrons give it unique bonding properties Can bond with other carbon very well Can make four bonds Elemental carbon can take different forms (Allotropes) Diamond Graphite Fullerenes

Diamond Allotropes are forms of an element that exist in the same state (solid, liquid or gas) but have different properties because their atoms are arranged differently. Diamond is one allotrope of carbon. Its properties include: Lustrous (shiny) Colourless and clear (transparent) Hard High melting point Insoluble in water (does not dissolve) Does not conduct electricity Talk about water’s shape and how they will learn why it’s that way

Diamond Diamond is used in jewellery because, when cut by experts, it will sparkle and reflect light in an attractive way. Diamond's hardness and high melting point make it useful for cutting tools, such as the diamond-tipped discs used to cut bricks and concrete. Talk about water’s shape and how they will learn why it’s that way

Diamond’s Structure and Bonding Diamond has a giant molecular structure. Each carbon atom is covalently bonded to four other carbon atoms. This makes diamond's melting point and boiling point very high. There are no free electrons or ions in diamond, so it does not conduct electricity. A lot of energy is needed to separate the atoms in diamond. This is because covalent bonds are strong, and diamond contains very many covalent bonds

Graphite Graphite is another allotrope of carbon. Like diamond, its properties include: Lustrous High melting point Insoluble in water However, unlike diamond, graphite is: Black and opaque (you cannot see through it) Slippery An electrical conductor Talk about water’s shape and how they will learn why it’s that way

Graphite Uses Graphite is used inside pencils. It slips easily off the pencil onto the paper and leaves a black mark. Graphite is also a component of many lubricants, for example bicycle chain oil, because it is slippery. Talk about water’s shape and how they will learn why it’s that way

Graphite’s Structure and Bonding In graphite each carbon atom is only covalently bonded to three other carbon atoms. Graphite contains layers of carbon atoms. Which can easily slide over each other because there are only weak forces between them. Graphite contains delocalised electrons allowing graphite to conduct electricity. Like diamond, graphite has a giant molecular structure. As its covalent bonds are very strong, and there are many of them, a lot of energy would be needed to separate atoms. This makes graphite's melting point and boiling point very high.

Fullerenes The fullerenes are a large class of allotropes of carbon and are made of balls, ‘cages’ or tubes of carbon atoms. Buckminster fullerene is one type of fullerene. Its molecules have 60 carbon atoms arranged in a hollow sphere. Buckminsterfullerene (or bucky-ball) is a spherical fullerene molecule with the formula C60. It has a cage-like fused-ring structure (truncated icosahedron) which resembles a soccer ball, made of twenty hexagons and twelve pentagons, with a carbon atom at each vertex of each polygon and a bond along each polygon edge. Nanotubes are fullerenes that can be used to reinforce graphite in tennis rackets because they are very strong. They are also used as semiconductors in electrical circuits. The nanotube's structure allows it to be used as a container for transporting a drug in the body. A molecule of the drug can be placed inside the nanotube cage. This keeps the drug 'wrapped up' until it reaches the site where it is needed. In this way, a dose that might be damaging to other parts of the body can be delivered safely to, for example, a tumour.

Carbon Nanotubes Carbon nanotubes could replace steel in tension in future technologies. A space elevator cable must carry its own weight as well as the additional weight of climbers. The required strength of the cable will vary along its length. This is because at various points it has to carry the weight of the cable below, or provide a downward force to retain the cable and counterweight above. Maximum tension on a space elevator cable is at geosynchronous altitude so the cable must be thickest there and taper carefully as it approaches Earth. Any potential cable design may be characterized by the taper factor – the ratio between the cable's radius at geosynchronous altitude and at the Earth's surface.[32] The cable must be made of a material with a large tensile strength/density ratio. For example, the Edwards space elevator design assumes a cable material with a specific strength of at least 100,000 kN/(kg/m).[2] This value takes into consideration the entire weight of the space elevator. An untapered space elevator cable would need a material capable of sustaining a length of 4,960 kilometers (3,080 mi) of its own weight at sea level to reach a geostationary altitude of 35,786 km (22,236 mi) without yielding.[33] Therefore, a material with very high strength and lightness is needed. For comparison, metals like titanium, steel or aluminium alloys have breaking lengths of only 20–30 km. Modern fibre materials such as kevlar, fibreglass and carbon/graphite fibre have breaking lengths of 100–400 km. Nanoengineered materials such as carbon nanotubes and, more recently discovered, graphene ribbons (perfect two-dimensional sheets of carbon) are expected to have breaking lengths of 5000–6000 km at sea level, and also are able to conduct electrical power.[citation needed] For high specific strength, carbon has advantages because it is only the 6th element in the periodic table. Carbon has comparatively few of the protons and neutrons which contribute most of the dead weight of any material. Most of the interatomic bonding forces of any element are contributed by only the outer few electrons. For carbon, the strength and stability of those bonds is high compared to the mass of the atom. The challenge in using carbon nanotubes remains to extend to macroscopic sizes the production of such material that are still perfect on the microscopic scale (as microscopic defects are most responsible for material weakness). [34] [35] [36] [37] As of 2014, carbon nanotube technology allowed growing tubes up to a few tenths of meters.[38]

Questions Why can graphite conduct electricity, but diamond cannot? Name a property of graphite that is different to carbon (excluding conductivity) Why is diamond used to cut granite (a very hard rock)?

Vocabulary Allotrope – A different arrangements of the atoms leading to different properties Insoluble – Unable to be dissolved impossible to solve.

Homework No Homework today. OH YEAH! impossible to solve.