2.2. Group 2 Metals.pdf

AQA Chemistry A-level 3.2.2: Group II - The Alkaline Earth Metals Detailed Notes This work by PMT Education is licensed under https://bit.ly/pmt-cc https://bit.ly/pmt-edu-cc CC BY-NC-ND 4.0...

AQA Chemistry A-level 3.2.2: Group II - The Alkaline Earth Metals Detailed Notes This work by PMT Education is licensed under https://bit.ly/pmt-cc https://bit.ly/pmt-edu-cc CC BY-NC-ND 4.0 https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc 3.2.2.1 - Group II The Group II metals lose two electrons to ​form 2+ ions​ when they react in order to achieve a full outer shell. Atomic Radius The atomic radius of group II metals ​increases​ down the group due to additional electron shells. Reactivity Increased electron ​shielding​ down the group makes the outer electrons ​easier to lose​. Therefore reactivity of the group II metals ​increases​ down the group. Ionisation Energy The first ionisation energy of group II metals ​decreases​ down the group due to a greater atomic radius and increased amounts of shielding. Melting Point The group II elements are ​metallic​ meaning the larger the ions within the metallic structure, the weaker the attractive forces as the attractive force has to ​act over a much greater distance​. Therefore the melting points ​decrease​ down the group. Reactions with Water The group II metals react with water in a redox reaction to produce a ​metal hydroxide and hydrogen​. The metal hydroxide form as an ​alkaline solution​, hence why the group II metals are known as the alkali metals. Example: The magnesium is oxidised from OS (oxidation state) 0 to OS +2. (Oxidation is loss of e-​ ​) Magnesium reacts very slowly in this way with liquid water, however the reaction can be much faster with steam​ as it provides the reaction with ​extra energy​. When steam is used, the magnesium burns with a ​bright white flame​ to form hydrogen and magnesium oxide, a ​white powder​. Example: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Solubility of Hydroxides The solubility of group II hydroxides varies and means these compounds have different uses. Solubility ​increases down the group​ meaning magnesium hydroxide (Mg(OH)​2​) is the least soluble and barium hydroxide (Ba(OH)​2​) the most soluble. As a result, magnesium hydroxide is used in medicine as an ​antacid​ as it is alkaline and can neutralise acids. It is used in a similar way in agriculture to neutralise acidic soils. Solubility of Sulfates Group II sulfates ​decrease in solubility down the group​ meaning magnesium sulfate (MgSO​4​) is the most soluble and barium sulfate (BaSO​4​) is the least soluble. The insolubility of ​barium sulfate​ means it is very useful in medicine as ​barium meals​. These are a form of medical tracer that allow internal tissues and organs to be imaged. Barium sulfate is toxic if it enters the bloodstream, however because it is insoluble, it ​cannot be absorbed​ into the blood. Therefore it is safe to use in this way. Barium chloride is used as a ​test for sulfate ions​ as it reacts to form barium sulfate which forms as a ​white precipitate​ when sulfate ions are present. Example: Metal Extraction Magnesium is used in the ​extraction of titanium​ from titanium chloride via a ​displacement reaction. Example: Flue Gas Removal Calcium oxide​ reacts with sulfur dioxide to remove it from factory pollutants and prevent it from being released into the atmosphere. This forms ​calcium sulfite and water​. Example: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc