chem chp 2

• reactivity

  attraction between electrons in outer shell + nucleus

  electrostatic attraction depends on:

  • distance between outer electrons + nucleus
  • number of inner shells
  • shielding affect - repeling outer shell -
  • easier / harder to gain / lose electron
• halogens

  form 1- ions

  form covalent compounds -

  sharing electrons with other non-metals more reactive can displace less reactive from solution of one of its salts

  reactivity decreases as you go down the group
• transition metals

  compared to g1:

  • higher melting points
  • higher densities
  • stronger
  • harder
  • less reactive don't really react with oxygen / water form colours

  important catalysts

  form differently charged ions
• group 1

  alkali metals

  very reactive

  reactivity increases as you go down the group

  low density, soft, shiny

  all form 1+ ions

  mostly white,

  dissolve in water - colourless solution

  melting points decrease as you go down the group

  react with water = hydrogen + metal hydroxide