4.1.4 Transition Metals

• The transition metals are located between Groups 2 and 3 in the centre of the periodic table
• They are very lustrous, they are hard, strong and are good conductors of heat and electricity
• They are highly dense metals and have very high melting points
• Transition metals can have more than one oxidation state  as they can lose a different number of electrons, depending on the chemical environment they are in

The transition elements on the Periodic table

The melting point, density and common ions of the elements Cr, Mn, Fe, Co, Ni and Cu are shown below

Transition Metals Table

• Compounds containing transition metals in different oxidation states will have different properties and colours in aqueous solutions

The colours produced by ions of the transition elements

• The transition metals are used extensively as catalysts which are substances that speed up the rate of a reaction without being used up in the process
• They do not take part in the reaction
• Their catalytic characteristics stem from their ability to interchange between a range of oxidation states
• This allows them to form complexes with reagents which can easily donate and accept electrons from other chemical species within a reaction system
• Common transition metal catalysts include:
  • Iron which is used in the Haber Process
  • Vanadium pentoxide (V₂O₅) which is used in the Contact Process to produce sulfuric acid
  • Nickel which is used in the hydrogenation of alkenes

• 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