Predicting Reactivity (OCR GCSE Combined Science A (Gateway))

Predicting Reactivity

• Using some of the patterns of reactivity in the Periodic Table we can predict what properties an element may have 

• Key patterns include:

  • Elements in Group 1 and 2 are highly reactive 

  • Metals in Group 1 and 2 get more reactive as you go down

  • Metals form ionic compounds with reactive non metals

  • Non- metals in Group 7 get less reactive as you go down 

  • Group 0 elements are unreactive

Comparison of Transition Metals and Group 1 Properties

• There are also some key differences between the reactivity of transition metals and Group 1 metals

• All of the group 1 metals form ions with a +1 charge while the transition metals can form ions with variable charges

  • For example iron can form an Fe²⁺ ion or an Fe³⁺ ion

• The transition metals are much harder, stronger and denser than the group 1 metals, which are very soft and light

• They have much higher melting points e.g. titanium melts at 1,688 ºC whereas potassium melts at only 63.5 ºC, not far off the average cup of tea!

• The transition metals are much less reactive than the group 1 metals

• The alkali metals react with water, oxygen and halogens while the transition metals either react very slowly or do not react at all

• A classic example of this is the reaction with oxygen

• A Group 1 metal will tarnish in the presence of oxygen as a metal oxide is formed

• When cut with a knife, the shiny appearance of the metal disappears in seconds as it is covered by the dull metal oxide

• Iron on the other hand can take several weeks to react with oxygen to form iron oxide (rust) and requires the presence of water