Transition Elements

The elements in which the differentiating electron enters the d-orbital of the penultimate shell are called d-block element. d-block elements are present in between electropositive s-block elements and electronegative p-block elements in the periodic table.

There are 4 series of d-block elements. First 3 series conation 10 elements each and fourth series is incomplete.

1. 3d series: present in IV period starting from Sc (21) to Zn (30)
2. 4d series: present in V period starting from Y (39) to Cd (48)
3. 5d series: present in VI period starting from La (57) to Hg (80)
4. 6d series: starts from Ac (89) and in complete. Present in VII period.

The d-block elements are also called transition elements, as they bring about the change from electropositive to electronegative in a gradual manner by being present in between s-block and p-block elements.

The outer electronic configuration of d-block elements is ns^1or2(n-1)d^1-10.

The transition elements exhibit the following typical characteristic properties due to small size, large nuclear charge and presence of d-electrons.

1. Variable oxidation states
2. Para and ferromagnetic properties
3. Formation of coloured hydrated ions and salts
4. Alloy formation
5. Catalytic properties
6. Complex formation