The chemistry of group 1 and 17

• group 1

  alkali metals
• alkali metals are highly reactive, soft, low-melting- points
• group 1 metals, M, react vigorously with oxygen to from basic oxides
• Group 1 metals, M, react vigorously with water to form a metal hydroxide and hydrogen.
• Group 17 halogens, X, react with Group 1 metals to form salts.
• reactions with oxygen and group 1 metals 


  4M+o2=2M2O
• reactions with water and group 1 metal

  2M(s) + 2H2O(l) 🡪 2MOH(aq) + H2(g)
• Group 17 halogens react with Group 1 metals

  2M(s) + X2(g) 🡪 2MX(s)
• Ionization energy decreases down group 1
• group 1 metal properties

  shiny when freshly cut, malleable, conduct electricity and heat
• the elements in group 1 are all reactive metals that readily react with oxygen, water and halogens
• Chemical and Physical Properties of group 1

  • Good conductors ofelectricity and heat
  • Low densities
  • Grey shiny surfaces when freshly cut with a knife
  • Very reactive metals
  • Form ionic compounds with non-metals
• Chemical and Physical Properties of group 17

  • Coloured
  • Show a gradual change from
  • gases (F2, Cl2), to liquid (Br2) and solids (I2, At2)
  • Very reactive non-metals
  • Form ionic compounds with metals
  • Form covalent molecules with other non-metals
• A more reactive halogen displaces a less reactive

  halogen from a solution/compound of one of its

  salts.
• the alkali metals react vigorously with oxygen (all tarnish rapidly in air) to form basic oxide that will dissolve in water to form an alkaline solution
• the alkali metals react rapidly with water to form hydrogen gas and metal hydroxide (alkaline solution)
• Hydroxides are strong bases and ionise completely in aqueous solution
• the reaction with water down group 1 becomes more vigorous as you go down the group
• the melting and boiling points of the halogens increase going down the group
• fluorine and chlorine are gases at room temperature and pressure bromine is a liquid and iodine is a solid
• metallic character increases down group 17 as the atoms get larger and ionisation energy decreases so that it becomes easier to form a positive ion
• all group 17 react either by gaining an electron to form a halide ion or by forming covalent compounds
• the reactivity in terms of the formation of x- ions can be related to a decrease in the magnitude of the electron affinity
• reactivity decreases down group 17
• the more reactive halogen displaces, the less reactive ehalogen is in the solution.
• oxidising agent

  a species that oxidises another species bt taking electrons from it
• reducing agent 


  a species that reduces another species by giving electrons to it
• why does the melting point decrease down group 1 ?


  As the ions get larger as we go down the group,

  the nucleus becomes further away from the delocalized electrons, and the attraction becomes weaker.

  This means that less energy is required to break apart the lattice going down to group 1.
• why does reactivity increases down group 1 


  because the ionisation energy decreases as the size of the atom increases