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A periodic table is a table that contains an arrangement of chemical elements. 

There are more than 100 chemical elements (118) identified so far in the world. So it is difficult to study each of them, understand them and remember them and their physical and chemical properties. Also it is difficult to discuss with other scientists and experts with out a common platform. 

The periodic table enlists the chemical elements in a logical order of atomic number. Atomic number is the number of protons or the number of electrons in an atom in that element.  

A row is called a period.  The atomic number increases in a period as you move from left to right and increases as you move from top to bottom.  A column is called a group.  The elements in a group have similar physical and chemical characteristics.  The group number increases from 1 to 18 as you move from left to right in a row.

The periodic table took a number of years to develop.  It was Mendeleev who published the first periodic table in 1869.   The current standard form of the table is attributed to HG Deming.  Seaborg published the placement of actinide elements in f block and synthesized them. He won the Nobel prize for that in 1951.

The first element in the table is Hydrogen (N = 1). The last one is Unanoctium (N=118). The s block (groups 1 & 2) and p block (groups 13 to 18) are most important. We study them in detail.  The remaining are more complicated and studied in advanced degrees.  The elements in between s & p block are called d block and those below d block are called f block. 

The atomic weight increases from left to right and from top to bottom. Atomic number increases by 2 for the second period, and by 8 for the 2nd and 3rd. It increases by 18 for the rest.

The elements in the rightmost 18 th group are called the inert or noble gases.  

The chemical properties are studied comparing one element with another in the same group or period. Atomic radius increases in a group from top to bottom. Atomic radius decreases from left to right in a period. Similarly metallic charactr, eletron affinity etc are studied.


There are other forms of periodic table made by different scientists in two dimensions, three dimensions and using colour also in a four dimensional table. There are also extensions with g block consisting of newly synthesized elements.  A spiral table developed by T Benfy in 1960 with Hydrogen at the center is a popular one.
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