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STRUCTURE & BONDING A guide for GCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING.

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Presentation on theme: "STRUCTURE & BONDING A guide for GCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING."— Presentation transcript:

1 STRUCTURE & BONDING A guide for GCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING

2 STRUCTURE & BONDING INTRODUCTION This Powerpoint show is one of several produced to help students understand selected GCSE Chemistry topics. It is based on the requirements of the AQA specification but is suitable for other examination boards. Individual students may use the material at home for revision purposes and it can also prove useful for classroom teaching with an interactive white board. Accompanying notes on this, and the full range of AS and A2 Chemistry topics, are available from the KNOCKHARDY WEBSITE at... All diagrams and animations in this Powerpoint are original and created by Jonathan Hopton. Permission must be obtained for their use in any commercial work.

3 STRUCTURE & BONDING OVERVIEW The following slides illustrate how the type of chemical bonding affects the physical properties of elements and compounds. To understand how the three main chemical bonds types are formed, view the powerpoint CHEMICAL BONDING available from the KNOCKHARDY SCIENCE GCSE WEBSITE at...

4 IONIC BONDING

5 IONIC BONDING RESULTS FROM THE ELECTROSTATIC ATTRACTION BETWEEN IONS OF OPPOSITE CHARGE.

6 IONIC BONDING IONIC BONDING RESULTS FROM THE ELECTROSTATIC ATTRACTION BETWEEN IONS OF OPPOSITE CHARGE. IONS ARE FORMED WHEN SPECIESGAIN ELECTRONS TO FORM NEGATIVE IONS (ANIONS)

7 IONIC BONDING IONIC BONDING RESULTS FROM THE ELECTROSTATIC ATTRACTION BETWEEN IONS OF OPPOSITE CHARGE. IONS ARE FORMED WHEN SPECIESGAIN ELECTRONS TO FORM NEGATIVE IONS (ANIONS) orLOSE ELECTRONS TO FORM POSITIVE IONS (CATIONS)

8 IONIC BONDING IONIC BONDING RESULTS FROM THE ELECTROSTATIC ATTRACTION BETWEEN IONS OF OPPOSITE CHARGE. IONS ARE FORMED WHEN SPECIESGAIN ELECTRONS TO FORM NEGATIVE IONS (ANIONS) orLOSE ELECTRONS TO FORM POSITIVE IONS (CATIONS) NOTE:THE ELECTRONS ARE NOT REALLY LOST BUT MOVE AWAY

9 IONIC BONDING IONIC BONDING RESULTS FROM THE ELECTROSTATIC ATTRACTION BETWEEN IONS OF OPPOSITE CHARGE. IONS ARE FORMED WHEN SPECIESGAIN ELECTRONS TO FORM NEGATIVE IONS (ANIONS) orLOSE ELECTRONS TO FORM POSITIVE IONS (CATIONS) NOTE:THE ELECTRONS ARE NOT REALLY LOST BUT MOVE AWAY WHEN METALS IN GROUPS I and II REACT WITH NON-METALS IN GROUPS VI and VII, IONIC COMPOUNDS ARE FORMED; SODIUM CHLORIDE IS THE BEST KNOWN EXAMPLE.

10 FORMATION OF SODIUM CHLORIDE ClCl SODIUM ATOM 2,8,1 Na CHLORINE ATOM 2,8,7 PRESS THE SPACE BAR TO START / ADVANCE AN ANIMATION

11 ClCl SODIUM ION 2,8 Na CHLORIDE ION 2,8,8 both species now have full outer shells; ie they have the electronic configuration of a noble gas + FORMATION OF SODIUM CHLORIDE

12 ClCl SODIUM ION 2,8 Na CHLORIDE ION 2,8,8 NaNa + + e¯ 2,8,1 2,8 ELECTRON TRANSFERRED C l + e¯ C l ¯ 2,8,7 2,8,8 + FORMATION OF SODIUM CHLORIDE

13 IONIC BONDING IN SODIUM CHLORIDE C l - chloride ion Na + sodium ion

14 IONIC BONDING IN SODIUM CHLORIDE C l - chloride ion Na + sodium ion SODIUM CHLORIDE HAS A REGULAR STRUCTURE - A GIANT IONIC LATTICE

15 IONIC BONDING IN SODIUM CHLORIDE C l - chloride ion Na + sodium ion SODIUM CHLORIDE HAS A REGULAR STRUCTURE - A GIANT IONIC LATTICE OPPOSITELY CHARGED IONS ARE HELD TOGETHER BY STRONG ELECTROSTATIC FORCES ACTING IN ALL DIRECTIONS

16 IONIC BONDING IN SODIUM CHLORIDE C l - chloride ion Na + sodium ion SODIUM CHLORIDE HAS A REGULAR STRUCTURE - A GIANT IONIC LATTICE OPPOSITELY CHARGED IONS ARE HELD TOGETHER BY STRONG ELECTROSTATIC FORCES ACTING IN ALL DIRECTIONS THERE IS NO SINGLE NaC l, JUST (EQUAL) VAST NUMBERS OF IONS

17 IONIC BONDING IN SODIUM CHLORIDE C l - chloride ion Na + sodium ion SODIUM CHLORIDE HAS A REGULAR STRUCTURE - A GIANT IONIC LATTICE OPPOSITELY CHARGED IONS ARE HELD TOGETHER BY STRONG ELECTROSTATIC FORCES ACTING IN ALL DIRECTIONS THERE IS NO SINGLE NaC l, JUST (EQUAL) VAST NUMBERS OF IONS YOU DO NOT GET MOLECULES OF SODIUM CHLORIDE

18 EACH SODIUM ION IS SURROUNDED BY SIX CHLORIDE IONS EACH CHLORIDE ION IS SURROUNDED BY SIX SODIUM IONS C l - Chloride ion Na + Sodium ion IONIC BONDING IN SODIUM CHLORIDE

19 PHYSICAL PROPERTIES OF IONIC COMPOUNDS VERY HIGH MELTING POINTS Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - IONS ARE HELD IN THE LATTICE BY THE STRONG ELECTROSTATIC FORCES A LOT OF ENERGY IS NEEDED TO SEPARATE THE IONS

20 PHYSICAL PROPERTIES OF IONIC COMPOUNDS VERY HIGH MELTING POINTS Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - IONS ARE HELD IN THE LATTICE BY THE STRONG ELECTROSTATIC FORCES A LOT OF ENERGY IS NEEDED TO SEPARATE THE IONS Na + Cl - Na + Cl - Na + Cl - Na + Cl - THE IONS HAVE MORE FREEDOM AND THE SODIUM CHLORIDE BECOMES LIQUID

21 PHYSICAL PROPERTIES OF IONIC COMPOUNDS SOLUBILITY IN WATER IONIC COMPOUNDS ARE USUALLY SOLUBLE IN WATER

22 PHYSICAL PROPERTIES OF IONIC COMPOUNDS SOLUBILITY IN WATER Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - IONIC COMPOUNDS ARE USUALLY SOLUBLE IN WATER Na + Cl - WATER IS A POLAR SOLVENT. THE HYDROGEN END IS SLIGHTLY POSITIVE AND THE OXYGEN END SLIGHTLY NEGATIVE. O H H O H H O H H O H H O H H O H H O H H O H H

23 PHYSICAL PROPERTIES OF IONIC COMPOUNDS SOLUBILITY IN WATER Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - IONIC COMPOUNDS ARE USUALLY SOLUBLE IN WATER Na + Cl - WATER IS A POLAR SOLVENT. THE HYDROGEN END IS SLIGHTLY POSITIVE AND THE OXYGEN END SLIGHTLY NEGATIVE. ALTHOUGH IT REQUIRES A LOT OF ENERGY TO SEPARATE THE IONS, THIS IS MORE THAN COMPENSATED FOR BY THE STABILISING EFFECT OF THE WATER SURROUNDING EACH ION O H H O H H O H H O H H O H H O H H O H H O H H

24 PHYSICAL PROPERTIES OF IONIC COMPOUNDS ELECTRICAL PROPERTIES Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - WHEN SOLID, THE IONS ARE NOT FREE TO MOVE NO CONDUCTION OF ELECTRICITY SOLID SOLID IONIC COMPOUNDS DO NOT CONDUCT ELECTRICITY

25 PHYSICAL PROPERTIES OF IONIC COMPOUNDS ELECTRICAL PROPERTIES Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - WHEN SOLID, THE IONS ARE NOT FREE TO MOVE NO CONDUCTION OF ELECTRICITY Na + Cl - Na + Cl - Na + Cl - Na + Cl - SOLID MOLTEN WHEN MOLTEN, THE IONS ARE FREE TO MOVE ELECTRICITY IS CONDUCTED MOLTEN IONIC COMPOUNDS DO CONDUCT ELECTRICITY

26 PHYSICAL PROPERTIES OF IONIC COMPOUNDS IONIC SOLIDS ARE BRITTLE

27 PHYSICAL PROPERTIES OF IONIC COMPOUNDS IONIC SOLIDS ARE BRITTLE IF YOU HIT A CRYSTAL OF SODIUM CHLORIDE WITH A HAMMER, THE CRYSTAL BREAKS INTO PIECES.

28 IF YOU MOVE A LAYER OF IONS, IONS OF THE SAME CHARGE END UP NEXT TO EACH OTHER. THE LAYERS REPEL EACH OTHER AND THE CRYSTAL BREAKS UP. PHYSICAL PROPERTIES OF IONIC COMPOUNDS IONIC SOLIDS ARE BRITTLE IF YOU HIT A CRYSTAL OF SODIUM CHLORIDE WITH A HAMMER, THE CRYSTAL BREAKS INTO PIECES.

29 METALLIC BONDING

30 METALS CONSIST OF GIANT STRUCTURES OF REPEATING IONS ARRANGED IN A REGULAR CRYSTAL LATTICE AND HELD TOGETHER BY A MOBILE CLOUD OR SEA OF ELECTRONS. Atoms arranged in a regular lattice

31 METALLIC BONDING METALS CONSIST OF GIANT STRUCTURES OF REPEATING IONS ARRANGED IN A REGULAR CRYSTAL LATTICE AND HELD TOGETHER BY A MOBILE CLOUD OR SEA OF ELECTRONS. Atoms arranged in a regular lattice The outer shell electrons of each atom leave to join a mobile cloud of electrons which holds the positive ions together.

32 METALLIC BONDING METALS CONSIST OF GIANT STRUCTURES OF REPEATING IONS ARRANGED IN A REGULAR CRYSTAL LATTICE AND HELD TOGETHER BY A MOBILE CLOUD OR SEA OF ELECTRONS. Atoms arranged in a regular lattice The outer shell electrons of each atom leave to join a mobile cloud of electrons which holds the positive ions together. THE ELECTRONS ARE SAID TO BE DELOCALISED (not confined to any one place)

33 PHYSICAL PROPERTIES OF METALS VERY GOOD CONDUCTORS OF ELECTRICITY For a substance to conduct electricity it must have mobile ions or electrons.

34 PHYSICAL PROPERTIES OF METALS VERY GOOD CONDUCTORS OF ELECTRICITY For a substance to conduct electricity it must have mobile ions or electrons. ELECTRONS CAN MOVE THROUGH

35 PHYSICAL PROPERTIES OF METALS VERY GOOD CONDUCTORS OF ELECTRICITY THE MOBILE ELECTRON CLOUD IN METALS PERMITS THE CONDUCTION OF ELECTRICITY For a substance to conduct electricity it must have mobile ions or electrons. ELECTRONS CAN MOVE THROUGH

36 PHYSICAL PROPERTIES OF METALS VERY GOOD CONDUCTORS OF HEAT THE MOBILE ELECTRON CLOUD IN METALS PERMITS THE CONDUCTION OF HEAT For a substance to conduct heat it must have mobile electrons. ELECTRONS CAN MOVE

37 PHYSICAL PROPERTIES OF METALS CAN BE BENT AND SHAPED Metals can have their shapes changed relatively easily

38 MALLEABLE CAN BE HAMMERED INTO SHEETS DUCTILE CAN BE DRAWN INTO RODS AND WIRES PHYSICAL PROPERTIES OF METALS CAN BE BENT AND SHAPED Metals can have their shapes changed relatively easily

39 MALLEABLE CAN BE HAMMERED INTO SHEETS DUCTILE CAN BE DRAWN INTO RODS AND WIRES As the metal is beaten into another shape the mobile electrons in the cloud continue to hold the positive ions together. Some metals, such as gold, can be hammered into sheets thin enough to be translucent. PHYSICAL PROPERTIES OF METALS CAN BE BENT AND SHAPED Metals can have their shapes changed relatively easily

40 PHYSICAL PROPERTIES OF METALS ALLOYS Alloys are usually made from two or more different metals.

41 Why use To improve the properties of metals; alloys? it usually makes them stronger PHYSICAL PROPERTIES OF METALS ALLOYS Alloys are usually made from two or more different metals.

42 Why use To improve the properties of metals; alloys? it usually makes them stronger How do The different sized atoms of the metals distort they work? the layers in the structure, making it more difficult for them to slide over each other and so make alloys harder than pure metals. PHYSICAL PROPERTIES OF METALS ALLOYS Alloys are usually made from two or more different metals.

43 Steel an alloy of IRON and CARBON (a non-metal!) - low-carbon steels are easily shaped - high-carbon steels are hard PHYSICAL PROPERTIES OF METALS ALLOYS - Examples Alloys are usually made from two or more different metals.

44 Steel an alloy of IRON and CARBON (a non-metal!) - low-carbon steels are easily shaped - high-carbon steels are hard - some steels contain other metals chromium / nickelstainless steel manganesevery hard for railway points tungstenvery hard for drill tips PHYSICAL PROPERTIES OF METALS ALLOYS - Examples Alloys are usually made from two or more different metals.

45 Steel an alloy of IRON and CARBON (a non-metal!) - low-carbon steels are easily shaped - high-carbon steels are hard - some steels contain other metals chromium / nickelstainless steel manganesevery hard for railway points tungstenvery hard for drill tips CopperPure copper, like gold and aluminium, is too soft for many uses. It is mixed with similar metals. Brasscopper / zinc Bronzecopper / tin Coinage metalcopper /nickel PHYSICAL PROPERTIES OF METALS ALLOYS - Examples Alloys are usually made from two or more different metals.

46 PHYSICAL PROPERTIES OF METALS SHAPE MEMORY ALLOYS Shape memory alloys can return to their original shape after being deformed

47 Shape memory alloy (SMA) can be deformed, and then returned to their original shape by the application of heat. PHYSICAL PROPERTIES OF METALS SHAPE MEMORY ALLOYS Shape memory alloys can return to their original shape after being deformed

48 Shape memory alloy (SMA) can be deformed, and then returned to their original shape by the application of heat. They are made of a NICKLEL-TITANIUM alloy - NITINOL Small amounts of other metals can be added to alter properties PHYSICAL PROPERTIES OF METALS SHAPE MEMORY ALLOYS Shape memory alloys can return to their original shape after being deformed

49 Shape memory alloy (SMA) can be deformed, and then returned to their original shape by the application of heat. They are made of a NICKLEL-TITANIUM alloy - NITINOL Small amounts of other metals can be added to alter properties ExamplesKey-hole surgery instruments Spectacle frames Thermostats Dental braces PHYSICAL PROPERTIES OF METALS SHAPE MEMORY ALLOYS Shape memory alloys can return to their original shape after being deformed

50 COVALENT BONDING

51 A covalent bond consists of… a shared pair of electrons with one electron being supplied by each atom either side of the bond. COVALENT BONDS ARE STRONG

52 COVALENT BONDING A covalent bond consists of… a shared pair of electrons with one electron being supplied by each atom either side of the bond. COVALENT BONDS ARE STRONG Covalent bond are found between the atoms in molecules. Molecules can be SIMPLE MOLECULESH 2, CO 2, CH 4 or GIANT MOLECULESdiamond, graphite, silica

53 SIMPLE COVALENT MOLECULES Covalent bonding between the atoms in each molecule is STRONG Bonding between individual molecules is not covalent and is WEAK STRONG COVALENT BONDS (hard to break) VERY WEAK ATTRACTION BETWEEN MOLECULES (easy to break) Because the attractions between molecules are very weak, simple covalent molecules usually have low melting and boiling points because it is easy to separate the molecules

54 SIMPLE COVALENT MOLECULES GENERAL PROPERTIES OF SIMPLE MOLECULES APPEARANCE gases, liquids or solids with low melting and boiling points MELTING POINT Very low Weak attractive forces between molecules means that very little energy is needed to move them apart ELECTRICAL Dont conduct electricity - have no mobile ions or electrons Covalent bonding between the atoms in each molecule is STRONG Bonding between individual molecules is not covalent and is WEAK

55 GIANT COVALENT MOLECULES In giant covalent molecules there are many atoms joined together in a regular arrangement by a very large number of covalent bonds.

56 GIANT COVALENT MOLECULES In giant covalent molecules there are many atoms joined together in a regular arrangement by a very large number of covalent bonds. GENERAL PROPERTIES OF GIANT MOLECULES MELTING POINT Very high structure is made up of a large number of covalent bonds, all of which need to be broken if atoms are to be separated

57 GIANT COVALENT MOLECULES In giant covalent molecules there are many atoms joined together in a regular arrangement by a very large number of covalent bonds. GENERAL PROPERTIES OF GIANT MOLECULES MELTING POINT Very high structure is made up of a large number of covalent bonds, all of which need to be broken if atoms are to be separated ELECTRICAL Dont conduct electricity - have no mobile ions or electrons BUT... Graphite conducts electricity GIANT MOLECULES = MACROMOLECULES = COVALENT NETWORKS They all mean the same! GIANT MOLECULES = MACROMOLECULES = COVALENT NETWORKS They all mean the same!

58 GIANT COVALENT MOLECULES In giant covalent molecules there are many atoms joined together in a regular arrangement by a very large number of covalent bonds. GENERAL PROPERTIES OF GIANT MOLECULES MELTING POINT Very high structure is made up of a large number of covalent bonds, all of which need to be broken if atoms are to be separated ELECTRICAL Dont conduct electricity - have no mobile ions or electrons BUT... Graphite conducts electricity STRENGTH Hard - exist in a rigid tetrahedral structure Diamond and silica (SiO 2 )... but Graphite is soft

59 GIANT COVALENT MOLECULES In giant covalent molecules there are many atoms joined together in a regular arrangement by a very large number of covalent bonds. GENERAL PROPERTIES OF GIANT MOLECULES MELTING POINT Very high structure is made up of a large number of covalent bonds, all of which need to be broken if atoms are to be separated ELECTRICAL Dont conduct electricity - have no mobile ions or electrons BUT... Graphite conducts electricity STRENGTH Hard - exist in a rigid tetrahedral structure Diamond and silica (SiO 2 )... but Graphite is soft GIANT MOLECULES = MACROMOLECULES = COVALENT NETWORKS They all mean the same! GIANT MOLECULES = MACROMOLECULES = COVALENT NETWORKS They all mean the same!

60 GIANT COVALENT MOLECULES DIAMOND MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms

61 GIANT COVALENT MOLECULES DIAMOND MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH STRONG each carbon atom is joined to four others in a rigid structure Coordination Number = 4

62 GIANT COVALENT MOLECULES DIAMOND MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH STRONG each carbon atom is joined to four others in a rigid structure Coordination Number = 4 ELECTRICAL NON-CONDUCTOR No free electrons - all 4 carbon electrons used for bonding

63 GIANT COVALENT MOLECULES DIAMOND MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH STRONG each carbon atom is joined to four others in a rigid structure Coordination Number = 4 ELECTRICAL NON-CONDUCTOR No free electrons - all 4 carbon electrons used for bonding

64 GIANT COVALENT MOLECULES GRAPHITE MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms layers can slide over each other - used as a lubricant and in pencils

65 GIANT COVALENT MOLECULES GRAPHITE MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH SOFT each carbon is joined to three others in a layered structure Coordination Number = 3 layers are held by weak intermolecular forces layers can slide over each other - used as a lubricant and in pencils

66 GIANT COVALENT MOLECULES GRAPHITE MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH SOFT each carbon is joined to three others in a layered structure Coordination Number = 3 layers are held by weak intermolecular forces can slide over each other ELECTRICAL CONDUCTOR Only three carbon electrons are used for bonding which leaves the fourth to move freely along layers layers can slide over each other - used as a lubricant and in pencils

67 GIANT COVALENT MOLECULES GRAPHITE MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH SOFT each carbon is joined to three others in a layered structure Coordination Number = 3 layers are held by weak intermolecular forces can slide over each other ELECTRICAL CONDUCTOR Only three carbon electrons are used for bonding which leaves the fourth to move freely along layers layers can slide over each other- used as a lubricant and in pencils

68 ANOTHER FORM OF CARBON FULLERENES Although not officially classed as giant molecules, fullerenes are made from carbon atoms joined together to make tubes and cages. (The prefix NANO means that everything is on a very small scale)

69 ANOTHER FORM OF CARBON NANOSCIENCE Refers to the science of structures that are 1–100nm in size Nanoparticles Show different properties to the same materials in bulk and have a high surface area to volume ratio This can lead to the development of… new computers new catalysts new coatings stronger and lighter construction materials new cosmetics such as sun-tan creams and deodorants Scientifically, NANO means one thousand millionth (10 -9 )

70 ANOTHER FORM OF CARBON FULLERENES Although not officially classed as giant molecules, fullerenes are made from carbon atoms joined together to make tubes and cages. NANOTUBESThese are fullerenes where hexagonal sheets of carbon atoms have been rolled into a tube – a bit like chicken wire

71 ANOTHER FORM OF CARBON FULLERENES Although not officially classed as giant molecules, fullerenes are made from carbon atoms joined together to make tubes and cages. NANOTUBESThese are fullerenes where hexagonal sheets of carbon atoms have been rolled into a tube – a bit like chicken wire sheets can be rolled to form tubes

72 ANOTHER FORM OF CARBON FULLERENES Although not officially classed as giant molecules, fullerenes are made from carbon atoms joined together to make tubes and cages. NANOTUBESThese are fullerenes where hexagonal sheets of carbon atoms have been rolled into a tube – a bit like chicken wire very strong useful where lightness and strength are needed eg tennis racket frames

73 ANOTHER FORM OF CARBON FULLERENES Although not officially classed as giant molecules, fullerenes are made from carbon atoms joined together to make tubes and cages. NANOTUBESThese are fullerenes where hexagonal sheets of carbon atoms have been rolled into a tube – a bit like chicken wire very strong useful where lightness and strength are needed eg tennis racket frames conductors of used as semiconductors in electronic circuits electricity

74 ANOTHER FORM OF CARBON FULLERENES Although not officially classed as giant molecules, fullerenes are made from carbon atoms joined together to make tubes and cages. NANOTUBESThese are fullerenes where hexagonal sheets of carbon atoms have been rolled into a tube – a bit like chicken wire very strong useful where lightness and strength are needed eg tennis racket frames conductors of used as semiconductors in electronic circuits electricity tubular can be used to transport a drug into the body structure drug molecules can be put inside the nanotube which holds the drug until it gets to where it is needed

75 ANOTHER FORM OF CARBON FULLERENES Although not officially classed as giant molecules, fullerenes are made from carbon atoms joined together to make tubes and cages. NANOTUBESThese are fullerenes where hexagonal sheets of carbon atoms have been rolled into a tube – a bit like chicken wire very strong useful where lightness and strength are needed eg tennis racket frames conductors of used as semiconductors in electronic circuits. electricity tubular can be used to transport a drug into the body structure drug molecules can be put inside the nanotube which holds the drug until it gets to where it is needed

76 ANOTHER FORM OF CARBON BUCKMINSTERFULLERENE A fullerene where the carbon atoms are arranged in a ball shape molecule C 60 Sixty carbon atoms are arranged in a ball in rings of 5 and 6 It is a bit like the arrangement of panels in a football

77 GIANT COVALENT MOLECULES SILICA MELTING POINT VERY HIGH many covalent bonds must be broken to separate atoms STRENGTH STRONG each silicon atom is joined to four oxygen atoms each oxygen atom is joined to two silicon atoms ELECTRICAL NON-CONDUCTOR – no mobile electrons silicon atoms oxygen atoms

78 © 2011 JONATHAN HOPTON & KNOCKHARDY PUBLISHING STRUCTURE & BONDING THE END


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