BMAT Ninja Chemistry- Chemical Bonding, Structure + Properties and Groups

What is an element a Substance that contains only ONE type of atom. What is a compound 2 or more elements chemically combined What is a mixture A combination of two or more substances that are not chemically combined (can be physically separated) What is the structure of ionic compounds giant ionic lattice with a regular arrangement How are the ions held together in ionic bonding? - by strong electrostatic forces of attraction Why do ionic compounds have high melting and boiling points? electrostatic forces require lots of energy to overcome Can ionic compounds conduct electricity? - when molten or in aqueous form - ions are free to move around and carry an electrical current What does a covalent bond represent one shared pair of electrons Why do macromolecules have high melting and boiling points? - covalent bonds requires lots of energy to break Why can graphite conduct electricity? -layer of delocalised electrons between the sheets of atoms can move and carry charge Why is graphite slippery - weak intermolecular forces between layers are easily overcome so layers can slide over each other Structure of metals - positive metal ions surrounded by a sea of delocalised electrons (which come from the outermost electron shells of the metal atoms) Why are metals good conductors of electricity and heat? delocalised electrons are free to move through structure carrying heat and charge How are metal atoms held together? electrostatic forces of attraction between positively charged metal ions and negatively charged delocalised electrons Why can metals be bent and shaped? regular structure within metals allows layers of atoms are able to slide over each other Why are alloys harder than pure metals? - disruption of metal structure due to different sized atoms means the layers of atoms can no longer easily slide over each other Uses and properties of metals: aluminium- low density and doesn't corrode- used in aeroplanes and foil Iron- strong but brittle so carbon usually added to form steel- an alloy Copper- good conductors and malleable- uses in electrical cables Silver- pretty jewellery but tarnishes Gold- pretty jewellery that doesn't tarnish. Also has some uses in dentistry Titanium- strong with low density- used in aeroplanes and artificial joints