Halides 

Transition metals react with halogens at high temperatures to form halides. These reactions have very high activation energies; therefore, high temperatures are required to start these reactions. However, once the reaction starts, the heat liberated is sufficient to sustain the reaction. The order of reactivity of different halogens decreases as:

Fluorides are usually ionic whereas chlorides, bromides and iodides are predominantly covalent. The covalent character increase in atomic mass of the halogen. For example, CuF₂ is ionic while CuCl₂ and CuBr₂ are covalent consisting of infinite chains. Co-ordination number of copper in these compounds is six.

Fluorine brings about the highest oxidation state of the metal. This is due its small size and high electronegativity. Halides of metals in higher oxidation states are relatively unstable and get hydrolysed easily. For example,
                                         
TiCl₄ + 2H₂O    TiO₂ + 4HCl

Sulphides

Sulphides of transition metals are prepared either by direct combination of sulphur with metals or by the reaction of H₂S or Na₂S with the solution of their salts. In sulphides, the oxidation state of metal is generally low because sulphur is a weak oxidising agent. These sulphides are generally coloured or black. For example, NiS, CoS and CuS are black, MnS is light pink and CdS is yellow. They are insoluble in water.

Example: classify the following oxides as acidic, basic and amphoteric:
                         
MnO, MnO₂, Mn₂O₃, Mn₃O₄, Mn₂O₇.

Solution: Acidic oxide : Mn₂O₇
               
Basic oxides : MnO, Mn₂O₃
      
Amphoteric oxides: Mn₃O₄, MnO₂.