Chemistry: The Periodic Table

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  • Chemistry: the periodic table
    • the history of the atom
      • plum pudding model, bohr model, nuclear atom
      • theories are adapted through time
    • atoms
      • nucleus contains protons and neutrons
      • nucleus has a positive charge from protons
      • electrons have no mass and are negative
      • protons = electrons
      • mass number - protons and neutrons
      • atomic number - protons
      • neutrons = atomic / mass
    • elements and isotopes
      • order of ascending atomic number
      • number of electrons in outer shell = group
      • isotopes have the same atomic number but different mass numbers
    • history of the periodic table
      • dobereiner organised elements into triads
      • newlands octaves put elements into rows
      • dmitiri mendeleev aranged elements with spaces for undiscovered
    • electron shells
      • electrons always occupy shells
      • 1st. 2 electrons 2nd. 8 electrons 3rd. 8 electrons
      • configuration2,8,8 = 12 =Mg
    • ionic bonding
      • atoms lose of gain electrons
      • attracted by opposite charges
      • metals and non metals form giant ionic structures
      • do not conduct electricity when solid
    • ions and ionic compounds
      • metals lose electrons to form positive ions
      • non metals gain electrons to form negative ions
      • non metals and a metal form an ionic bond
      • if 2 electrons lost, charge is 2+
      • dot and cross shows ionic bonding
    • covalent bonding
      • covalent bonds share electrons
      • hydrogen atoms share electrons with one another
      • carbon teams up with four hydrogens
      • chlorine atoms share electrons with one another
      • water is oxygen covalently bonding with two hydrogen atoms
      • carbon dioxide is one carbon and two oxygen atoms
    • alkali metals
      • lower in group 1 - more reactive elements
      • more reactive due to easily lost electron
      • properties: low melting point, low density, very soft
      • oxidation is the loss of metals
      • alkali metals oxidize because they only have one outer electron
      • lithium - red flame
      • sodium - orange flame
      • potassium - lilac flame
    • halogens
      • fluorine, chlorine, bromine, iodine, astatine
      • as you go down, less reactive elements
      • chlorine: reactive, poisonous, dense green gas
      • bromine: dense, poisonous, orange liquid
      • iodine: dark grey crystalline solid
      • reduction is the gain of electrons
      • halogen + alkali = salt
    • metals
      • all metals have same basic qualities
      • held together by metallic bonds
      • movement of free electrons
      • very hard, dense, and lustrous
      • high melting and boiling points
      • strong yet malleable
      • good conductors of heat and energy due to free electrons
    • superconductors and transition metals
      • all metals have some electrical resistance
      • if a metal is made cold enough the resistance dissapears
      • could start a current and need no energy
      • disadvantages: expensive to produce cold temperatures, cannot make room temperature
      • transition metals are in the centre of the periodic table
      • transitions make good catalysts
    • thermal decomposition and precipitation
      • when a substance breaks down due to heat
      • transition metal carbonates break down
      • a precipitate is an insoluble substance formed in a liquid
      • precipitation is a test for transition metal ions
      • copper oxide - blue
      • iron oxide - grey/green
      • iron hydroxide - orange/brown
    • water puroty
      • limited water resources in UK: surface water, ground water
      • water is purified in treatment plants
      • filtration - wire mesh
      • sedimentation - chemicals added to remove clumps
      • chlorination -  gas to kill bacteria
      • tap water may contain: nitrate, lead, pesticide residues
    • testing water puroty
      • 1) add hydrochloric acid
      • 2) add ten drops of barium chloride
      • 3) white precipitate means sulfate ions
      • 1) add nitric acid
      • 2) add ten drops of silver nitrate
      • 3) any precipitate means halide ions

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