unit 1.6 periodicity

• what is periodicity

  repeating pattern across different periods or down different groups e.g. ionisation energy, melting and boiling point and electronegativity
• whats metallic bonding

  • attraction between metal ion and a delocalised electron holds the shape
• melting and boiling point down group 1

  • decreases
  • bigger atoms, attraction to delocalised electrons decreases, more shielding larger atomic radii. atoms are more easily pulled apart
  • metal ion holds shape as the nucleus are attracted to delocalised electrons
• across a period (Na-Mg)

  • number of delocalised electrons increases and nuclear charge increases, stronger attraction
  • Mg has stronger metallic bonding than Na
• down group 7 increases

  • size of atom determines boiling and melting point, number of van der waals increases as atom gets bigger
  • more van der waals harder to break apart atoms
  • individual van der waals are weak but stronger as theres more
• electronegativity

  • a measure of the ability of an atom in a molecule to attract electrons in a covalent bond to itself
  • increases across periodic table, more protons- stronger nuclear attraction
  • decreases down periodic table, more shells- increased shielding
• what does oxidised mean

  oxidation number increases
• what does reduced mean

  oxidation number decreased
• whats a redox reaction

  when something gets reduced and oxidised in the same reaction
• flame test colour for lithium

  red
• flame test colour for sodium

  yellow/orange
• flame test colour for pottasium

  lilac
• flame test colour for magnesium

  colourless
• flame test colour for calcium

  brick red
• flame test colour for barium

  apple green
• flame test colour for strontium

  crimson
• flame test colour for copper

  blue
• group 1 reaction with water

  • lithium floats on the water, gently fizzes
  • sodium melts into a ball that dashes around the surface
  • pottasium melts into a ball and catches fire
  • caesium explodes and shatters a glass container
• group 2 reaction with water

  • calcium, steady stream of bubbles and goes cloudy white
  • barium, prodcues more effervescence and solution is clearer as barium hydroxide is more soluble
• group 2 nitrates

  all soluble
• group 2 carbonates

  all insoluble
• group 2 sulfates

  • magnesium is soluble, barium is insoluble
  • less soluble as you go down
  • use, barium sulfate used as a medical tracer, allows internal organs to be imaged
  • barium chloride test for sulfate ions
• group 2 hydroxides

  • magnesium hydroxide is insoluble, barium hydroxide is soluble
  • hydroxides get more soluble as you go down the group
• group 2 hydroxides decompose

  • more heat to break down
  • thermal stability of compound increases harder to decompose them (down a group)
• group 2 carbonates decomposes

  • same trend as hydroxides
  • thermal stability increases down a group more heat required
• group 7 reactivity

  • reactivity decreases down group
  • gains electrons to become ions
  • why trend is seen; atomic radius increases, electron shielding and nuclear attraction decreases
• 2 experiments to show difference in reactivity

  • reaction with iron wool
  • displacement reaction using halogens and silver nitrate
• reaction with iron wool

  Cl- dont heat Cl, heat iron wool, brown gas

  Br- heat to break van der waals, glows

  I- heat to break van der waals, barely glows
• oxidising agent

  oxidising ability decreases down the group wiht fluorine being the strongest