Allotropes of CarbonAllotropes of Carbon

DiamondGraphite“Buckyballs” or buckminsterfullerene

DiamondGraphite“Buckyballs” or buckminsterfullerene

Allotrope definitionAllotrope definition

Different structural/crystalline forms of the same element

Different structural/crystalline forms of the same element

DiamondDiamond

Each carbon atom is bonded to 4 others to form a giant covalent network or lattice

Each carbon atom is bonded to 4 others to form a giant covalent network or lattice

DiamondDiamond

Each carbon atom is bonded to 4 others to form a giant covalent network or lattice

Is bond is of the same length and equally strong so the carbon atoms are sp3 hybridized

Each carbon atom is bonded to 4 others to form a giant covalent network or lattice

Is bond is of the same length and equally strong so the carbon atoms are sp3 hybridized

DiamondDiamond

Each carbon atom is bonded to 4 others to form a giant covalent network or lattice

Is bond is of the same length and equally strong so the carbon atoms are sp3 hybridized

As all the electrons are localised (fixed in position), diamond is exceptionally hard and it does not conduct electricity

Each carbon atom is bonded to 4 others to form a giant covalent network or lattice

Is bond is of the same length and equally strong so the carbon atoms are sp3 hybridized

As all the electrons are localised (fixed in position), diamond is exceptionally hard and it does not conduct electricity

DiamondDiamond

From: ibchem.com/IB/ibnotes/full/bon_htm/14.4.htm

Properties of DiamondProperties of Diamond

Very high melting point

Doesn’t conduct electricity

Very hard

Very high melting point

Doesn’t conduct electricity

Very hard

GraphiteGraphite

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

GraphiteGraphite

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

As each bond is the same, the carbon atoms are sp2 hybridised

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

As each bond is the same, the carbon atoms are sp2 hybridised

GraphiteGraphite

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

As each bond is the same, the carbon atoms are sp2 hybridised

The remaining p orbital electron is delocalised to form weak bonds between the layers

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

As each bond is the same, the carbon atoms are sp2 hybridised

The remaining p orbital electron is delocalised to form weak bonds between the layers

GraphiteGraphite

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

As each bond is the same, the carbon atoms are sp2 hybridised

The remaining p orbital electron is delocalised to form weak bonds between the layers

The covalent layer lattice has all sigma bonds

Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

As each bond is the same, the carbon atoms are sp2 hybridised

The remaining p orbital electron is delocalised to form weak bonds between the layers

The covalent layer lattice has all sigma bonds

GraphiteGraphite

From: http://physics.bu.edu/cc104/covalent.html From: http://physics.bu.edu/cc104/covalent.html

GraphiteGraphite

Because of the layers, graphite is an excellent lubricant as the layers can slide over each other

Because of the layers, graphite is an excellent lubricant as the layers can slide over each other

GraphiteGraphite

Because of the layers, graphite is an excellent lubricant as the layers can slide over each other

Graphite is also a good conductor of electricity because of the delocalised electrons e.g. carbon rods, lead pencils

Because of the layers, graphite is an excellent lubricant as the layers can slide over each other

Graphite is also a good conductor of electricity because of the delocalised electrons e.g. carbon rods, lead pencils

BuckminsterfullereneBuckminsterfullerene

Is one member of a family of spherical carbon molecules sometimes called “buckyballs”

Has the formula C60

The C atoms are arranged in hexagons and pentagons to give a geodesic spherical structure similar to a football

Is one member of a family of spherical carbon molecules sometimes called “buckyballs”

Has the formula C60

The C atoms are arranged in hexagons and pentagons to give a geodesic spherical structure similar to a football

BuckminsterfullereneBuckminsterfullerene

From: www.vega.org.uk/video/programme/65

Vancouver GeodesicVancouver Geodesic

From: http://www.flickr.com/photos/sharply_done/416104996/

BuckminsterfullereneBuckminsterfullerene

Like in graphite, each carbon atom is bonded to 3 others

Like in graphite, each carbon atom is bonded to 3 others

BuckminsterfullereneBuckminsterfullerene

Like in graphite, each carbon atom is bonded to 3 others

Each carbon atom is sp2 hybridized

Like in graphite, each carbon atom is bonded to 3 others

Each carbon atom is sp2 hybridized

BuckminsterfullereneBuckminsterfullerene

Like in graphite, each carbon atom is bonded to 3 others

Each carbon atom is sp2 hybridized

There are also delocalized electrons, hence C60 can conduct electricity slightly

Like in graphite, each carbon atom is bonded to 3 others

Each carbon atom is sp2 hybridized

There are also delocalized electrons, hence C60 can conduct electricity slightly

From: www.nanomaterialsdiscovery.com/technology.php...

Silicon Silicon dioxide - SiO2

From: http://www.galleries.com/minerals/elements/silicon/silicon.htm , www.fiji.hotel-pictures.com/.../beach2.html

Silicon Silicon dioxide - SiO2

From: http://www.galleries.com/minerals/elements/silicon/silicon.htm , www.fiji.hotel-pictures.com/.../beach2.html

Structure of SiliconStructure of Silicon

Silicon contains 4 valence electrons

It forms a lattice similar to that of diamond - each Si atom bonded to 4 others

Silicon is fairly unreactive and acts as an insulator at low temperatures as it has no free electrons

With impurities added it can conduct electricity at low temperatures

Silicon contains 4 valence electrons

It forms a lattice similar to that of diamond - each Si atom bonded to 4 others

Silicon is fairly unreactive and acts as an insulator at low temperatures as it has no free electrons

With impurities added it can conduct electricity at low temperatures

From: http://web1.caryacademy.org/chemistry/rushin/StudentProjects/ElementWebSites/silicon/Structure.htm

Structure of silicon dioxideStructure of silicon dioxide

Commonly known as silica and seen as sand or quartz

Like diamond, SiO2 is also a giant covalent lattice/ structure

Each Si atom is bonded to 4 O atoms, and each O atom is bonded to 2 Si atoms

Commonly known as silica and seen as sand or quartz

Like diamond, SiO2 is also a giant covalent lattice/ structure

Each Si atom is bonded to 4 O atoms, and each O atom is bonded to 2 Si atoms

From: http://www.moe.gov.sg/edumall/tl/digital_resources/chemistry6.htm , http://electronics.howstuffworks.com/quartz-watch2.htm

Properties of silicon dioxide

Properties of silicon dioxide

has a high melting point - varying depending on what the particular structure is (remember that the structure given is only one of three possible structures), but around 1700°C. Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs.

is hard. This is due to the need to break the very strong covalent bonds.

doesn't conduct electricity. There aren't any delocalised electrons. All the electrons are held tightly between the atoms, and aren't free to move

is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and the silicon or oxygen atoms which could overcome the covalent bonds in the giant structure.

has a high melting point - varying depending on what the particular structure is (remember that the structure given is only one of three possible structures), but around 1700°C. Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs.

is hard. This is due to the need to break the very strong covalent bonds.

doesn't conduct electricity. There aren't any delocalised electrons. All the electrons are held tightly between the atoms, and aren't free to move

is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and the silicon or oxygen atoms which could overcome the covalent bonds in the giant structure.