Question

Explain the following:
3d, 4d, and 5d series consists of 10 elements each.

Answer 1

Hint:The D-block total 4 series are present 3d, 4d, 5d and 6d series. The 6d series is incomplete and 3d, 4d and 5d consists of 10 elements each. The d-orbital contains 5-orbital, each one can be filled by two electrons.

Complete step by step answer:The elements which are present in the periodic table from the third group to the twelfth group are considered as D-block elements. The valence electrons of these elements lie in the d-orbital of the electronic configuration. The first three rows of D-block are referred to as 3d, 4d and 5d series.
The D-block elements are also known as the transition metal element because of the partially filled d-orbital but all the D-block elements do not have partially filled d-orbital.
The elements scandium and yttrium belong to group 3. They have partially filled d-orbital, therefore they are considered as transition elements. The elements like zinc, cadmium and mercury belong to 12 columns of the D-block consisting of completely filled d-orbital, therefore they are not considered as transition metal elements.
Thus, all transition metal elements are D-block elements but all D-block elements are not transition metal elements.
The general electronic configuration of D-block elements is $(n - 1){d^{1 - 10}}n{s^{1 - 2}}$. The elements of this block are stable after achieving partially filled d-orbital or completely filled d-orbital. The maximum of 10 electrons can be filled in the d-orbital, thus each series consists of only 10 elements.

Note:In D-block elements due to partially filled d-orbital d-d transition is observed in which the electrons get excited by observing visible light and due to this these elements show different colour.