Introduction

When you see the periodic table anywhere you always take it for granted that it is very easy to arrange the elements in rows and column but the fact is, it took the thousands of years to arrange these elements in specific order. so lets discuss one by one how scientists arranged it.

1. Dobereiner’s classification of Triads

He was a German Chemist - who proposed the idea of Triads. According to Triads he arranged three elements in a column on the basis of atomic masses - in the triads the central atom has the atomic mass of average of other two elements. In this table you can see the atomic mass of sodium is the average of atomic mass lithium and potassium. Same goes for Bromine and Strontium.

• Law of Octaves

Newland put forward this law, according to this law elements are arranged in increasing order of atomic mass.

According to this law he said every 8th element has similar properties to 1st element, 9th element similar to 2nd element.

Table Newlands Classification octaves

1. LI=7 Be=94 B=11 C=12 N=14 O=16 F=19

2. Na=23 Mg=24 Al=27.3 Si=28 P=32 Cl=35.5

Lithium has similar properties to sodium and Beryllium has similar to Magnesium and so on.

• Mendeleev's Periodic Classification

In 1869 he arranged elements in periods and groups according to their physical and chemical properties.

• Lother Meyer’s Classification

He published the Periodic table and arranged 56 elements in 9 column according to atomic masses.