AQA Chemistry A-level 3.2.4: Period 3 Elements Detailed Notes PDF

AQA Chemistry A-level 3.2.4: Period 3 Elements 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 3.2.4: Period 3 Elements 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 3.2.4.1 - Properties Period 3 Metals Sodium and magnesium both react ​ionically​ to form positive ions. Sodium reacts to form 1+ ions whereas magnesium forms 2+ ions. Example: Sodium is ​more reactive​ than magnesium as it only has to lose one electron to form an ion, whereas magnesium has to lose two electrons. Therefore​ less energy is required​ to ionise sodium making it more reactive. This means the reaction above with magnesium is ​slow​. However the speed of reaction can be increased by using​ steam​ instead of water. Steam provides the reaction with greater energy resulting in a ​violent reaction ​in which magnesium burns with a ​bright white flame​. It produces hydrogen and magnesium oxide. Example: Period 3 Oxides The period 3 elements react with oxygen to form ​oxides​ with each element in their ​highest oxidation state​. This number is often the same as the group number. Example: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc It is very useful to learn the oxides that form from the ​period 3 elements​: Sulfur can also react to form SO​3​ with an oxidation state of +6 but this requires ​high temperatures and a catalyst​. These oxides have different ​structures and bonding ​that affects the ​reactivity​ and ​melting points ​of the compounds: Oxide Structure and Relative Melting Reactivity Bonding Point (​o​C) Na​2​O Ionic ≈ 1250 Vigorous MgO Ionic ≈ 2750 Vigorous Al​2​O​3 Ionic ≈ 2000 Slow (covalent character) (faster if powdered) SiO​2 Macromolecular ≈ 1500 Slow P​4​O​10 Simple covalent ≈ 500 Vigorous SO​2 Simple covalent ≈ -10 Burns steadily https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Reactions with Water The ​ionic oxides​ combine with water to form ​alkaline solutions​ with a pH around 10-14. Examples: The ​simple covalent oxides​ of sulfur and phosphorus combine with water to form ​acidic solutions​ with a pH around 0-2. Examples: When in solution, these acids ​dissociate into H​+​ ions​ and ions of ​conjugate base​. Acid-base Reactions Basic, ionic oxides react with acids to produce a ​salt and water​. This is a ​neutralisation reaction. Examples: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Acidic, covalent oxides react with bases to produce a ​salt and water​ in a ​neutralisation reaction. Example: The bonding in​ aluminium oxide​ is partially ionic and covalent meaning it is ​insoluble​ in water as the ions don’t dissociate. This also means it can act as both an acid and a base, known as amphoteric​. It reacts as both to form a ​salt and water​ in neutralisation reactions. Examples: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc