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

STRUCTURESTRUCTURE& BONDING& BONDINGA guide for GCSE studentsA guide for GCSE students

2010 2010 SPECIFICATIONSSPECIFICATIONSKNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING

STRUCTURE & BONDINGSTRUCTURE & 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...

www.knockhardy.org.uk

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.

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.

STRUCTURE & BONDINGSTRUCTURE & BONDING

OVERVIEWOVERVIEW

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...

www.knockhardy.org.uk/gcse.htm

IONIC IONIC BONDINGBONDING

IONIC BONDING

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

IONIC BONDING


IONS ARE FORMED WHEN SPECIES GAIN ELECTRONS TO FORMNEGATIVE IONS (ANIONS)

IONIC BONDING



or ‘LOSE’ ELECTRONS TO FORMPOSITIVE IONS (CATIONS)

IONIC BONDING




NOTE: THE ELECTRONS ARE NOT REALLY ‘LOST’ BUT MOVE AWAY

IONIC BONDING




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.

FORMATION OF SODIUM CHLORIDEFORMATION OF SODIUM CHLORIDE

Cl

SODIUM ATOM2,8,1

Na

CHLORINE ATOM2,8,7

PRESS THE SPACE BAR TO START / ADVANCE AN ANIMATION

Cl

SODIUM ION2,8

Na

CHLORIDE ION2,8,8

both species now have ‘full’ outer shells; ie they have the electronic configuration of a noble gas

+


Cl

SODIUM ION2,8

Na

CHLORIDE ION2,8,8

Na Na+ + e¯2,8,1 2,8

ELECTRON TRANSFERRED

Cl + e¯ Cl¯2,8,7 2,8,8

+


IONIC BONDING IN SODIUM CHLORIDEIONIC BONDING IN SODIUM CHLORIDE

Cl- chloride ion

Na+ sodium ion


Cl- chloride ion

Na+ sodium ion

SODIUM CHLORIDE HAS A REGULAR STRUCTURE - A GIANT IONIC LATTICE


Cl- chloride ion

Na+ sodium ion


OPPOSITELY CHARGED IONS ARE HELD TOGETHER BY STRONG ELECTROSTATIC FORCES ACTING IN ALL DIRECTIONS


Cl- chloride ion

Na+ sodium ion



THERE IS NO SINGLE NaCl , JUST (EQUAL) VAST NUMBERS OF IONS


Cl- chloride ion

Na+ sodium ion



THERE IS NO SINGLE NaCl , JUST (EQUAL) VAST NUMBERS OF IONS

YOU DO NOT GET MOLECULES OF SODIUM CHLORIDEYOU DO NOT GET MOLECULES OF SODIUM CHLORIDE

EACH SODIUM ION IS SURROUNDED BY SIX CHLORIDE IONS

EACH CHLORIDE ION IS SURROUNDED BY SIX SODIUM IONS

Cl- Chloride ion Na+ Sodium ion


PHYSICAL PROPERTIES OF IONIC COMPOUNDSPHYSICAL PROPERTIES OF IONIC COMPOUNDS

VERY HIGH MELTING POINTSVERY 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


VERY HIGH MELTING POINTSVERY 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


SOLUBILITY IN WATERSOLUBILITY IN WATERIONIC COMPOUNDS ARE USUALLY SOLUBLE IN WATER


SOLUBILITY IN WATERSOLUBILITY 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.

OH

H

OH H

OH

H

OH H

O H

H

OH

H

OH H

OH H


SOLUBILITY IN WATERSOLUBILITY 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

OH

H

OH H

OH

H

OH H

O H

H

OH

H

OH H

OH H


ELECTRICAL PROPERTIESELECTRICAL PROPERTIES

Na+Cl- Na+Cl-

Na+Cl-Na+ Cl-

Na+Cl- Na+Cl-

WHEN SOLID, THE IONS ARE NOT FREE TO MOVE

NO CONDUCTIONOF ELECTRICITY

SOLID

SOLID IONIC COMPOUNDS DO NOT CONDUCT ELECTRICITYSOLID IONIC COMPOUNDS DO NOT CONDUCT ELECTRICITY


ELECTRICAL PROPERTIESELECTRICAL PROPERTIES

Na+Cl- Na+Cl-

Na+Cl-Na+ Cl-

Na+Cl- Na+Cl-

WHEN SOLID, THE IONS ARE NOT FREE TO MOVE

NO CONDUCTIONOF 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 ELECTRICITYMOLTEN IONIC COMPOUNDS DO CONDUCT ELECTRICITY


IONIC SOLIDS ARE BRITTLEIONIC SOLIDS ARE BRITTLE



IF YOU HIT A CRYSTAL OF SODIUM CHLORIDE WITH A HAMMER, THE CRYSTAL BREAKS INTO PIECES.

+ +

+ ++ +

+ +- -- -

- -

- -

+ +

+ +

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.



IF YOU HIT A CRYSTAL OF SODIUM CHLORIDE WITH A HAMMER, THE CRYSTAL BREAKS INTO PIECES.

METALLIC METALLIC BONDINGBONDING

METALLIC BONDINGMETALLIC 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 arrangedin 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 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)

PHYSICAL PROPERTIES OF METALSPHYSICAL PROPERTIES OF METALS

VERY GOOD CONDUCTORS OF ELECTRICITYVERY GOOD CONDUCTORS OF ELECTRICITY

For a substance to conduct electricityit must have mobile ions or electrons.




ELECTRONS CAN MOVE THROUGH



THE MOBILE ELECTRON CLOUD IN METALSPERMITS THE CONDUCTION OF ELECTRICITY


ELECTRONS CAN MOVE THROUGH


VERY GOOD CONDUCTORS OF HEATVERY GOOD CONDUCTORS OF HEAT

THE MOBILE ELECTRON CLOUD IN METALSPERMITS THE CONDUCTION OF HEAT

For a substance to conduct heatit must have mobile electrons.

ELECTRONS CAN MOVE


CAN BE BENT AND SHAPEDCAN BE BENT AND SHAPED

Metals can have their shapes changed relatively easily

MALLEABLE CAN BE HAMMERED INTO SHEETS

DUCTILE CAN BE DRAWN INTO RODS AND WIRES




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 hammeredinto sheets thin enough to be translucent.





ALLOYSALLOYS

Alloys are usually made from two or more different metals.

Why use To improve the properties of metals;alloys? it usually makes them stronger


ALLOYSALLOYS


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.


ALLOYSALLOYS


Steel an alloy of IRON and CARBON (a non-metal!)- low-carbon steels are easily shaped- high-carbon steels are hard


ALLOYS - ExamplesALLOYS - Examples



- some steels contain other metals chromium / nickel stainless steel manganese very hard for railway points

tungsten very hard for drill tips





- some steels contain other metals chromium / nickel stainless steel manganese very hard for railway points

tungsten very hard for drill tips

Copper Pure copper, like gold and aluminium, is too softfor many uses. It is mixed with similar metals.

Brass copper / zincBronze copper / tinCoinage metal copper /nickel





SHAPE MEMORY ALLOYSSHAPE MEMORY ALLOYS

Shape memory alloys can return to their original shape after being deformed

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





They are made of a NICKLEL-TITANIUM alloy - ‘NITINOL’

Small amounts of other metals can be added to alter properties

Examples Key-hole surgery instrumentsSpectacle framesThermostatsDental braces




COVALENT COVALENT BONDINGBONDING

COVALENT BONDINGCOVALENT BONDING

A covalent bond consists of…

a shared pair of electrons with one electron beingsupplied by each atom either side of the bond.

COVALENT BONDS ARE STRONGCOVALENT BONDS ARE STRONG

COVALENT BONDINGCOVALENT BONDING

A covalent bond consists of…

a shared pair of electrons with one electron beingsupplied by each atom either side of the bond.

COVALENT BONDS ARE STRONGCOVALENT BONDS ARE STRONG

Covalent bond are found between the atoms in molecules.

Molecules can be SIMPLE MOLECULES H2, CO2, CH4

or GIANT MOLECULES diamond, graphite, silica

SIMPLE COVALENT MOLECULESSIMPLE COVALENT MOLECULES

Covalent bonding between the atoms in each molecule is STRONG

Bonding between individual molecules is not covalent and is WEAK

STRONGCOVALENT

BONDS

(hard to break)

VERY WEAK ATTRACTIONBETWEEN 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

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

SIMPLE COVALENT MOLECULESSIMPLE COVALENT MOLECULES

GENERAL PROPERTIES OF SIMPLE MOLECULESGENERAL PROPERTIES OF SIMPLE MOLECULES

APPEARANCE gases, liquids or solids with low melting and boiling points

MELTING POINT Very lowWeak attractive forces between molecules means that verylittle energy is needed to move them apart

ELECTRICAL Don’t 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

GIANT COVALENT MOLECULESGIANT 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 MOLECULESGENERAL PROPERTIES OF GIANT MOLECULES

MELTING POINT Very highstructure is made up of a large number of covalent bonds,all of which need to be broken if atoms are to be separated





ELECTRICAL Don’t conduct electricity - have no mobile ions or electronsBUT... Graphite conducts electricity

GIANT MOLECULES = MACROMOLECULES = COVALENT NETWORKSGIANT MOLECULES = MACROMOLECULES = COVALENT NETWORKS

They all mean the same!








STRENGTH Hard - exist in a rigid tetrahedral structureDiamond and silica (SiO2)... but

Graphite is soft


DIAMONDDIAMOND

MELTING POINT VERY HIGHmany covalent bonds must be broken to separate atoms


DIAMONDDIAMOND


STRENGTH STRONGeach carbon atom is joined to four others in a rigid structureCoordination Number = 4


DIAMONDDIAMOND


STRENGTH STRONGeach carbon atom is joined to four others in a rigid structureCoordination Number = 4

ELECTRICAL NON-CONDUCTORNo free electrons - all 4 carbon electrons used for bonding


GRAPHITEGRAPHITE


layers can slide over each other -used as a lubricant and in pencils


GRAPHITEGRAPHITE


STRENGTH SOFTeach carbon is joined to three others in a layered structureCoordination Number = 3layers are held by weak intermolecular forces



GRAPHITEGRAPHITE


STRENGTH SOFTeach carbon is joined to three others in a layered structureCoordination Number = 3layers are held by weak intermolecular forcescan slide over each other

ELECTRICAL CONDUCTOROnly three carbon electrons are used for bonding whichleaves the fourth to move freely along layers



GRAPHITEGRAPHITE


STRENGTH SOFTeach carbon is joined to three others in a layered structureCoordination Number = 3layers are held by weak intermolecular forcescan slide over each other

ELECTRICAL CONDUCTOROnly three carbon electrons are used for bonding whichleaves the fourth to move freely along layers

layers can slide over each other- used as a lubricant and in pencils

ANOTHER FORM OF CARBONANOTHER FORM OF CARBON

FULLERENESFULLERENES

Although not officially classed as giant molecules, fullerenes aremade from carbon atoms joined together to make tubes and cages.

(The prefix NANO means that everything is on a very small scale)


NANOSCIENCENANOSCIENCE

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 computersnew catalystsnew coatingsstronger and lighter construction materialsnew cosmetics such as sun-tan creams and deodorants

Scientifically, NANO means one thousand millionth (10-9)




NANOTUBES These are fullerenes where hexagonal sheets of carbon atomshave been rolled into a tube – a bit like ‘chicken wire’





sheets can be ‘rolled’to form tubes





very strong useful where lightness and strength are neededeg tennis racket frames






conductors of used as semiconductors in electronic circuitselectricity






conductors of used as semiconductors in electronic circuitselectricity

tubular can be used to transport a drug into the body structure

drug molecules can be put inside the nanotube whichholds the drug until it gets to where it is needed






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 whichholds the drug until it gets to where it is needed


BUCKMINSTERFULLERENEBUCKMINSTERFULLERENE

A fullerene where the carbon atoms are arranged in a ball shape molecule

C60 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


SILICASILICA


STRENGTH STRONGeach silicon atom is joined to four oxygen atomseach oxygen atom is joined to two silicon atoms

ELECTRICAL NON-CONDUCTOR – no mobile electrons

silicon atoms

oxygen atoms

© 2011 © 2011 JONATHAN HOPTON & KNOCKHARDY PUBLISHINGJONATHAN HOPTON & KNOCKHARDY PUBLISHING

STRUCTURESTRUCTURE& BONDING& BONDING

THE ENDTHE END

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

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