Structures and Properties 0.0 / 5 ? ChemistryStructures and PropertiesGCSEAQA Created by: carmen.lauCreated on: 06-10-15 16:41 Periodic Table Elements in Group 8 are also called noble gases, because they are mainly unreactive The further down each column you go, the less reactive the element Metals are on the left, non metals on the right Atomic mass: The number of protons and neutrons in the nucleus Always the bigger number Atomic (proton ) number: Number of protons Also the number of electrons (before bonding) 1 of 9 Ionic Bonding Bonding between 1 metal and 1 non- metal Where one atom gives electrons to the other atom This gives them both full outer shells, so they become less reactive Eg. Sodium + Chloride = Sodium chloride 2 of 9 Covalent Bonding Between 2 non- metals Can be written as 'H-H' or 'O=O' (double bond) Electrons are shared between atoms to give both atoms full outer shells Eg. Hydrogen + Oxygen = Hydrogen Oxide (water) 3 of 9 Metallic Bonding Semi-metals: Have some metal and some non- metal properties Semi metals sit on the line between metals and non- metals (Periodic table) Metals: Metals form giant structures Delocalised electrons in the outer shells are free to move between ions The bond is describing the bond between the free electrons and the ions These bonds are strong so that the metal can maintain it's shape and have a high melting/ boiling point Properties: Lustrous, Hard High density (Heavy for their size) High tensile strength (Resist being stretched) High melting/ boiling points 4 of 9 Bonds between Atoms and Molecules Intramolecular Forces: Atoms are held together by strong covalent bonds Intermolecular Forces: Forces between the molecules are weak 5 of 9 SMAs & Polymers Shape Memory Alloys: 2 solid phases The alloy can change between the phases depending on an electrical current or temperature Used in braces, glasses, robots etc. Polymers: Polymer- large molecule made of an identical repeating unit Monomer- The repeating unit that the polymer is made of 6 of 9 LDPE & HDPE LDPE: Low density poly (ethene) Flexible, soft Used for bags, cling film etc. Molecules are highley branched- loosely packed Formed from ethene using high pressures & a trace of oxygen HDPE: High density poly (ethene) Stiff, harder Used for buckets, bottles etc Formed from ethene in a catalyst at 50 degrees C with raised pressures Packed closer together Higher softening temperature & stronger than LDPEs 7 of 9 Thermosoftening & Thermosetting Plastics Thermosoftening: Plastic softens when heated & hardens when cooled The polymer molecules can slide over each other They can be easily stretched or moulded into a shape They retain their new shape after heating Thermosetting: Covalent bonds are formed between chains of the polymers when heated These give the material a high melting point & increased strength and rigidity They also prevent the plastics from being softened with heat Stronger & not as flammable Don't melt when heated 8 of 9 Nanoparticles Measured in nanometres (nm), a billionth of a metre Nanoparticles between 1 and 100 nm Can occur naturally (volcanic ash) or by accident ( combustion) Used in car bumpers to make the parts stronger Used in aluminium to make it more wear resistant Can cut greenhouse gases to prevent climate change Can improve energy storage and efficiency and purify polluted air May be health risks that havent been found yet Atomic weapons could be more accessible Expensive and difficult to develop 9 of 9
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