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C3 REVISION NOTES
EARLY PERIODIC TABLE
When scientists arranged elements in order of their atomic weights they found similar
properties at regular intervals.
Mendeleev produces a table that became the basis for the modern periodic table.
The early tables of elements were based on atomic weights (relative atomic mass).
THE MODERN PERIODIC TABLE
The modern periodic table is based on atomic numbers.
Elements within a group have similar chemical properties.
The reactivity of metals increases going down a group.
The reactivity of non metals decreases going down a group.
GROUP 1 THE ALKALI METALS
The elements in group 1 are all metals that form positive ions with a charge of +1. They react
with water to produce hydrogen and an alkali.
Going down the group: reactivity increases, melting and boiling points decrease.
The alkali metals form only ionic compounds in which their ions have a single positive charge.
GROUP 7 THE HALOGENS
The elements in group 7 are all non-metals with low melting and boiling points.
They form compounds with metals and non-metals.
The reactivity of the halogens decreases going down the group.
Halogens form ionic compounds with metals and covalently bonded compounds with
THE TRANSITION ELEMENTS
The elements between Groups 2 and 3 in the periodic table are called the `transition
Transition elements are all metals with high densities.
Many transition metals form several different ions and compounds that are coloured.
Transition metals ad their compounds are useful as catalysts.
All transition elements are metals that form positive ions with various charges. For example,
copper can form Cu+ and Cu2+ ions.
STRONG AND WEAK ACIDS/ALKALIS
Strong acids and alkalis ionise completely in aqueous solutions.
Weak acids and alkalis only partly ionise in aqueous solutions.
Acids are proton donors and bases are proton acceptors.
Titrations can be used to find the volumes of acids and alkalis that react completely.
A suitable indicator is used to show the end point of a titration.
The end point of a titration is when the acid and alkali have reacted completely.
Weak acid+ strong alkali use phenolphthalein
Weak alkali +strong acid use methyl orange
The concentrations of solutions can be calculated from titration data.
Concentrations are usually measured in moles per cubic decimetre (dm3) pr in grams per dm3.
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WATER AND SOLUBILITY
Many ionic compounds and some molecular substances dissolve in water.
A saturated solution has dissolved the maximum amount of solute at a given temperature.
Water vapour cannot be seen.
Solubility curves show how solubility changes with temperature.
The solubility of most solids increases with increasing temperature.
The solubility of gases decreases with increasing temperature.
Dissolved salts, usually of magnesium and calcium cause hard water.
Soap reacts with the dissolved salts to form scum.…read more
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Lithium = bright red
Sodium = golden yellow
Potassium = lilac
Calcium= brick red
Barium = green
Magnesium = no colour
Aluminium, calcium and magnesium ions form a white precipitate when mixed with hydroxide.
Al3+(aq) + 3OH-(aq) Al(OH)3(S)
Copper hydroxide is blue
Iron (II) hydroxide is green and slowly turns brown.
Iron (III) hydroxide is reddish brown
Ammonium ions react with sodium hydroxide solution to form ammonia. If solution is warmed
ammonia gas is given off and turns damp red litmus paper blue.…read more
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Spectroscopic methods depend on different substances absorbing different types of