C3 OVERVIEWWhat we have covered....

PERIODIC TABLE Early: arranged according to properties. Failed to take account of undiscovered

elements Mendelev’s table was the first to leave

gaps for unknown elements and formed the basis of the modern periodic table

Modern: arranged according to proton number

We can now explain the trends in groups due to electron number and shell energy

GROUP 1- ALKALI METALS Alkali metal + water metal hydroxide

+ H2

Reactivity increases as you go down the table

Form ions with 1+ charge

GROUP 7 - HALOGENS Diatomic molecules Form ions of 1- charge Form covalent compounds (share

electrons) with other non-metals Reactivity decreases as you go down the

group

THE TRANSISTION ELEMENTS Found in the middle of the periodic table High m.p’s and high b.p’s Good conductors of heat and electricity Do not react vigorously with oxygen or

water Compounds are usually coloured Can have a number of valencies (e.g

Fe2+, Fe3+)

Transition Metal electron config In an atom, as you get further from the nucleus

energy levels get closer together, until they start to overlap. This first happens between energy levels 3 and 4, and affects the way the shells fill up.

Potassium has 19 electrons, but the 19th goes in the 4th energy level not the 3rd.(2,8,8,1). Ca is 2,8,8,2.

The next ten elements (transition metals) put their electrons into the overlapping 3rd energy level until it is full.

Sc Ti V Cr Mn Fe Co Ni Cu2,8,9,2 2,8,10,

22,8,11,2

2,8,13,1

2,8,13,2

2,8,14,2

2,8,15,2

2,8,16,2

2,8,17,1

Sc Ti V Cr Mn Fe Co Ni Cu

2,8,9,2 2,8,10,2

2,8,11,2

2,8,13,1

2,8,13,2

2,8,14,2

2,8,15,2

2,8,16,2

2,8,17,1

STRONG AND WEAK ALKALIS Acids produce H+ ions in water Alkalis produce OH- ions in water

Strong acids/alkalis are 100% ionised (dissociated) in water – give more ions to solution

Weak acids/alkalis are only partly ionised in water – don’t give many ions to the solution.

Acids are proton DONORS Alkalis are proton ACCEPTORS

TITRATION Used to measure accurately how much

acid is need to completely neutralise an known amount of alkali (and vice versa).

Indicators are used to show the END POINT

TITRATION CALCULATIONS Mass = Mr x moles

Moles = concentration x volume

Use ratio of moles from the equation

Concentration units = mol/dm3

WATER AND SOLUBILITY Water evaporates from rivers and

oceans, and condenses in clouds, returning to the surface as rain (water cycle).

Most IONIC substances are soluble in water

Most COVALENT compounds are NOT soluble in water

A SATURATED solution contains the maximum amount of solute that will dissolve at that temperature.

SOLUBILITY CURVES The solubility of most solid solutes

INCREASES with temperature. The solubility of GASES DECREASES with

temperature.

Solubility curves show how the solubility changes with temperatureALWAYS CHECK AND STATE THE UNITS IN

ANSWERS!!

HARD WATER Dissolves metal compounds (usually

group 2) Mg and Ca make water hard Ca and Mg react with soap to form

SCUM Ca and Mg salts decompose on heating

leading to SCALE formation.

Hard water is good for your health!

REMOVING HARDNESS Soften water by removing the salts that

produce scum and scale

Washing Soda Ca2+ (aq) + CO3

2-(aq) CaCO3(s)

Ion Exchange columnExchanges Ca and Mg for softer Na ions.

WATER TREATMENT Making water safe to drink requires

removing microorganisms and decreasing levels of dissolved substances.

Filtering removes solids Adding chlorine kills bacteria

Pure water is obtained by DISTILLATION

COMPARING ENERGY CONTENT When fuels burn they react with oxygen

and release ENERGY – exothermic reaction.

A simple calorimeter can be used to measure the energy changes.However these will not give an ACCURATE

reading of energy released, they will allow different fuels to be compared.

TOO Much HEAT is lost to the surroundings

ENERGY CHANGES IN REACTIONS Energy is required to BREAK bonds Energy is RELEASED when bonds are

formed.

Exothermic reactions have a net energy RELEASE and are NEGATIVE in sign

Endothermic reaction have a net energy ABSORPTION and are POSITIVE in sign

Activation energy is the amount of energy required to START a reaction.

ENERGY CALCULATIONS E = mcT Where c is the specific heat capacity of

water 4.2 J/g/oC m is the mass of the liquids involved in

the reaction.

Remember: All energy must be quoted in kJ/mol!

TESTS FOR POSITIVE IONSUnknown

Red/brown

Cu 2+

Ammonia gasGiven off

Green/Brown

Add NaOH

NH 4+

Soluble

InsolubleColoured Ppt

Light blue

Fe 3+

Mg 2+Ca 2+

Fe 2+

Al 3+

Flame Test

Brick Red No colour

White Ppt

TESTS FOR NEGATIVE IONS

Add HCl

Fizzes

Add Warm NaOH

Add silver nitrateand dilute HNO3

No Fizz

Milky/Cloudy

LimewaterTest

No gasAmmoniasmell, turns Litmus blue

Cream ppt

Add Barium Chloride

CO3 -

White ppt

SO4 2-

Br -Cl - I -

White ppt Yellow ppt NO3 -

Add Al powder

and warmNH4

+

TESTING FOR ORGANIC SUBSTANCES Bromine water to test for saturation

Know how to determine the empirical formula from masses of carbon dioxide and water

produced through combustion of organic substances.

INSTRUMENTAL ANALYSIS

Some instrumental methods are suited to identifying elements, such as atomic absorption spectroscopy

used in the steel industry. Other instrumental methods are suited

to identifying compounds, such as infrared spectroscopy, ultraviolet

spectroscopy, nuclear magnetic resonance spectroscopy, and gas-liquid chromatography.

Some methods can be adapted for elements or compounds, such as mass spectrometry.