Elements located in d-block (Group 3 to 12) in the periodic table are called transition elements. These elements exhibit several characteristic properties, which set them apart from other elements. Some of their properties are as follows.
Transition elements generally possess high densities due to their higher atomic masses and closely packed structures. For example, iron(Fe) has a density of 7.87 g/cm³, tunguston(W) has a density of 19.3g/cm².
Transition elements have high melting points. This is because their metallic bonding is stronger, which in tern is due to the presence of partially filled d-sub shells. For example tunguston has a melting point of 3422 °C, platinum(Pt) has a melting point of 1768 °C.
Transition elements exhibit multiple oxidation states. This is because of d-sub shell can also participate in bonding along with s-sub shell. For example, iron(Fe) has oxidation states +2 and +3, copper(Cu) has oxidation states +1 and +2.
Transition elements often exhibit vibrant colours. For example, copper compounds appear blue or green, chromium compounds are often red or green.
Transition metals and their compounds are widely used as catalyst in various industrial processes. For example,
(a) Iron is used in the Haber Process for the synthesis of ammonia.
(b) Platinum and palladium are used as catalyst in catalytic converters to reduce harmful emissions in automobiles and industrial units.
(c) Nickel is used as catalyst in the manufacture of margarine.
(d) Platinum is used as catalyst in the contact process for the manufacture of sulphuric acid.