Structure 3.1.4 - trends in properties of elements down a group include the increasing metallic character of group 1 elements and the decreasing non-metallic character of group 17 elements
see 3.1.1 periods, groups and blocks
group 1: alkali metals
chemical properties:
- reactive metals
- reactivity increases down the group
- form ionic compounds
physical properties: - conductive of electricity and heat
- low density
- lustrous when not oxidised
named due to reaction with water producing hydroxide ions (a proton acceptor)
group 17: halogens
chemical properties:
- reactive non-metals
- reactivity decreases down the group
- form ionic compounds and covalent compounds
physical properties: - coloured
- show gradual change from gases to liquid solids
exist as diatomic molecules
reactivity explained by readiness to accept electrons
displacement reactions
the relative reactivity can be seen by placing them in competition for an extra electron eg
a chlorine nucleus has a stronger attraction for an electron than a bromine nucleus, so it takes the electron from the bromide ion, forming the chloride ion.