Introduction to the Periodic Table
The Periodic table is an arrangement of elements in the order of their increasing atomic numbers to show that elements
have related properties. Earlier tables, such as those of Dmitry Mandeleev (photograph) (1869) and Lother Meyer
(1869-70) were based on atomic weights which are measured as bulk properties and valency relationships. At that time the
concept of atomic numbers was unknown.
The main purpose of the periodic table was:
Classification of elements on the basis of electronic configuration:
From the view point of electronic configuration the elements can be subdivided into four major sub groups. They can be
classified as s,p,d and f block elements.
1. s-block elements : These have two atoms and include groups I A & II A. They contain one or two electrons in
their outer S-orbital. Strongly electropositive metals. The group I A elements are alkali metals. Elements with
two electrons in the outer orbit are called alkaline earth metals.
2. p-block elements : The elements from groups III A to VII A are included in this type. These are generally non-metals.
These elements are generally non-conductors with the exception being Silicon and Germanium which
are semi-conductors.
3. d-block elements : These are the elements in which the last electron is placed in d-orbital of penultimate energy
level. These elements are also known as transitional elements. All are metallic and have high melting and boiling
points. Good conductors of heat and energy.
4. f-block elements : The transition elements in which pre-penultimate f-sub orbital is being filled up are called
as inner-transition elements.
There are two series of these elements :
1) Lanthanides & 2) Actinides. Their compounds are colored and
are usually paramagnetic.
5. zero-group elements : Earlier these elements were known as inert or Noble gases. They are chemically unreactive.
They are incapable of forming any chemical compounds.
Reading the Periodic Table :
Figure 2 shows that each box in periodic table contains the following data: