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chemistry unit 2: - Coggle Diagram
chemistry unit 2:
ionic bonding
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the transfer of electron from metal atoms to non metal atoms. the metal atoms lose electrons to become positively charged ions and non metals gain electrons to become negatively charged.
ionic bonds are strong electrostatic force of attraction between the positive metal ion and the negative non metal ion.
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example: 2Na+Cl2 -> 2NaCl - sodium group one so one electron in outer shell, chlorine group 7. one chlorine molecule contains two chlorine atoms. each sodium atom transfers one electron to one of the chlorine atoms. all four atoms now have eight electrons in their outer shell.
properties
ionic compounds = giant structures of ions held by strong electrostatic attractions that act in all directions between oppositely charged ions
high melting and boiling points, do not conduct electricity when slid because ions cannot move but do conduct electricity when molten or in a solution as charged ions are free to move and carry their charge.
metallic bonding
occurs in both metals and alloys. have a giant structure in which electrons in the outer shell are delocalised - provides a regular arrangement (lattice) of positive ions held together by electrostatic attraction to the delocalised electrons. A metallic bond is the attraction between positive ions and delocalised negatively charged electrons.
properties
very strong and most have a high melting and boiling points. delocalised electrons = good thermal and electrical conductors. pure metals = regular arrangement = slide over each other easily = metals can be bent and shaped.
copper = water pipes, electrical wiring, sauce pans = unreactive and doesn't corrode with water, ductile, malleable, good conductivity.
aluminium - high voltage power cables, furniture, drink cans, food foil wrap. = corrosion resistant. ductile and malleable, good conductivity, low density.
gold - jewellery, electrical junctions = shiny, ductile, good conductivity.
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covalent bonding
shared pair of electrons between atoms. they occur in non metals and compounds of non metals. e.g. chlorine to bind with other chlorine - an electron from each atom is shared and therefore completes the outer shell (chlorine in group 7)
simple molecules - no overall electrical charge and cannot conduct electricity. usually liquids and gases with low melting and boiling points because of weak intermolecular forces. larger the molecule the stronger the intermolecular forces are.
giant covalent structures - strong covalent bonds which have to be broken for substance to melt or boil.
diamond - carbon. giant covalent lattice. each atom binds to four others. very hard substance with high melting point with no charged particles so it cant conduct electricity.
graphite - giant covalent structure and high melting point. each atom bonds to three others - layered hexagonal structure held together by weak intermolecular forces which can slide over each other making it soft and slippery. one electron from each carbon atom is delocalised which allow graphite to conduct heat and electricity.
silicon dioxide - similar to diamond. oxygen atom joined to two silicon atoms and each silicon atom is joined to four oxygen atoms.
graphene - form of carbon - single layer of graphite. arranged in hexagonal structure and is one atom thick. strong, good thermal and electrical conductor and is nearly transparent. electronics and composite materials.
fullerenes - carbon. structure based off hexagonal rings of carbon atoms. hollow shapes including tubes balls and cages. first fullerene = Buckminster fullerene C60. - most symmetrical and most stable fullerene.
Nano tubes - cylindrical and useful in nanotechnology electronics and materials.
also used to deliver drugs in the body in lubricants such as catalysts.
polymers - large molecules - synthetic plastic. strong covalent bonds. intermolecular forces are strong. solid at room temperature. polyethylene is produce when ethene molecules are joined together in an an addition polymerisation reaction. it is cheap and strong and is used to make plastic bottles and bags.
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nanoparticles
only a few hundred atoms. nanostructures combined. can be manipulated so materials can be developed that have new and specific properties. nanoparticle properties diff to same material in bulk. e.g more sensitive to light and heat and magnesium.
used in sun cream - better skin coverage and more effective protection from the suns ultraviolet rays. concern that it can get into and damage human cells or cause problems for the environment.
development of: - new drug delivery systems - synthetic skin for burn victims - computers and technology - catalysts for fuel cells - stronger and lighter construction materials - new cosmetics and deodorants - fabrics that prevent the growth of bacteria.
