Transition elements have
These properties come from the partly filled 3d sub-level. The 4s and 3d energy levels are close together, so a transition metal can lose different numbers of electrons and has variable oxidation states: iron forms Fe2+ and Fe3+, and chromium ranges from +2 to +6.The high melting and boiling points come from strong metallic bonding: a lattice of positive metal ions is held together by a sea of delocalised electrons, and transition metals can delocalise both their 4s and 3d electrons.Transition metals and their compounds are good catalysts because they can change oxidation state and can use their d orbitals to bond weakly to reactants. A heterogeneous catalyst provides a surface: the reactants adsorb onto it, bonds within the reactants break, new bonds form and the products desorb. Examples are iron in the Haber process, nickel in the hydrogenation of vegetable oils to make margarine and vanadium(V) oxide in the Contact process. Compounds of s-block metals, such as MgO and Na2O, have only one oxidation state and are poor catalysts, whereas Cr2O3 is a useful one.Transition metal ions also bond to ligands to form complex ions, and these are usually coloured.
- Relatively high densities compared to group 1 to group 3 metals
- High melting and boiling points
- form complex ions
- form coloured ions
- good catalysts
- can have variable oxidation states
These properties come from the partly filled 3d sub-level. The 4s and 3d energy levels are close together, so a transition metal can lose different numbers of electrons and has variable oxidation states: iron forms Fe2+ and Fe3+, and chromium ranges from +2 to +6.The high melting and boiling points come from strong metallic bonding: a lattice of positive metal ions is held together by a sea of delocalised electrons, and transition metals can delocalise both their 4s and 3d electrons.Transition metals and their compounds are good catalysts because they can change oxidation state and can use their d orbitals to bond weakly to reactants. A heterogeneous catalyst provides a surface: the reactants adsorb onto it, bonds within the reactants break, new bonds form and the products desorb. Examples are iron in the Haber process, nickel in the hydrogenation of vegetable oils to make margarine and vanadium(V) oxide in the Contact process. Compounds of s-block metals, such as MgO and Na2O, have only one oxidation state and are poor catalysts, whereas Cr2O3 is a useful one.Transition metal ions also bond to ligands to form complex ions, and these are usually coloured.