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Unit 4 Fact Sheet Bromine and mercury are the only 2 liquid elements Elements can be split into 2 group: metals and non metals (using zigzag line) Metals conduct electricity, non metals do not conduct (except carbon- graphite) When metals conduct the outer electrons move from one atom to the next State symbols: s = solid, l = liquid, g= gas and aq= aqueous (in solution) Compounds can be ionic or covalent Ionic compounds contain metal and non-metal elements Covalent compounds contain only non metal elements Ionic compounds contain ions Ions are atoms with a charge An ion is formed when atoms gain or lose electrons Metals lose electrons and become positive Non metals gain electrons and become negative Atoms give away or gain electrons to become like the noble gases because noble gases are very stable. The attractive force between ions of opposite charge is known as an ionic bond. Ionic compounds are always solid at room temperature Ionic solids exist as network/lattices of oppositely charged ions Covalent compounds can be solid, liquid or gas at room temperature Covalent compounds never conduct electricity Ionic compounds do not conduct when are solid but do conduct when they are melted or in solution. Covalent bonding involves atoms sharing electrons. The 2 positive nuclei are held together by their common attraction for the shared pair of electrons A solute is a substance which can be dissolved in a liquid. A solvent is a liquid which dissolves other substances. A solution is the mixture formed when a substance dissolves in a solvent. Electrical energy chemically changes a solution when it conducts A DC power supply must be used to identify the products Electrolysis means breaking up a compound into its elements using electricity The metal is formed at the negative rod because metal ions have a positive charge The non-metal is formed at the positive rod because non metals have a negative charge Covalent compounds cannot be electrolysed as they do not contain ions Very reactive metals can be extracted from their compounds by electrolysis In a battery the energy change is chemical energy to electrical energy Batteries go flat when the chemicals are used up Batteries are portable and expensive, the mains supply is cheap but not portable. Some batteries are rechargeable (eg lead acid battery) An electrolyte is a liquid in which conduction takes place by ions moving (it is needed to complete the circuit) Electricity can be produced by connecting different metals together (with an electrolyte) to form a cell. The movement of the ions in the ion bridge is to provide ions to complete the circuit The colour of an ionic compound is related to the colour of the positive and negative ions