EL 7 notes 

We get ions as a full outer shell of electrons leads to a more stable electron arrangement. Elements will lose or gain electrons to achieve this. ==Cations== = positive ions formed through losing electrons ==Anions== = negative ions formed from gaining electrons

Acid + metal = salt + hydrogen gas Acid + base = salt + water Acid + alkali = salt + water Acid + metal carbonate = salt + water + carbon dioxide Also you can get displacement reactions with a more reactive metal

• If a base dissolves in water it is an alkali
• All alkalis dissolve in water to produce OH- ions   Insoluble ionic substances are – barium, calcium, lead and silver sulphate’s. Silver and lead halides, all metal carbonates and all metal hydroxides except group 1 hydroxides and ammonium hydroxides.

==Test for sulphate ions== – adding barium chloride produces barium sulphate which is a white precipitate ==Test for halides ions== – adding silver nitrate results in the following precipitates. White = chloride ions. Cream = bromide ions. Yellow = iodide ions ==Testing for positive metal ions== – adding sodium hydroxide and a precipitate is seen Cu 2+ = blue precipitate Fe 2+ = green precipitate Fe 3+ = orange/brown precipitate Ca 2+ = white precipitate Mg 2+ = white precipitate Al 3+ = white precipitate that is dissolved in excess NaOH ==Test for lead ions== = add potassium iodide and a bright yellow precipitate is formed