periodic classification of elements

father of periodic table- Mendeleev

The arrangement of the known elements in certain groups in such a way so that the elements with similar properties are grouped together is known as classification of elements.


periodic classification

1)Lavoisier:-
classified the elements into metals and non- metals.


2)
Dobereinier’s Triads:-In 1829, Dobereinier a German chemist arranged certain elements with similar properties in groups of three in such a way that the atomic mass of the middle element was nearly the same as the average atomic masses of the third element.

Ex- atomic mass Li=7 ;Na=23 ;K=39
Atomic mass of Na=(7+39)/2=46/2=23
But only few elements could be covered under triads.
way that the atomic mass of the middle element was nearly the same as the average atomic masses of the third element.
Ex- atomic mass Li=7 ;Na=23 ;K=39
Atomic mass of Na=(7+39)/2=46/2=23
But only few elements could be covered under triads.

3)Newland’s law of octaves:- When elements are arranged in order to increasing atomic masses, every eight element has properties similar to first, just like musical notes.

4)
Lother’s Mayer’s atomic volume curve:- In 1869 Lother mayer plotted a graph b/w atomic volume of the elements and their atomic mass and he pointed that the elements with similar properties occupy similar position in the curve.

5)Mendeleev’s Periodic law:- The physical and chemical property of the elements are the periodic function of their atomic masses.
“Mendeleev’s arranged the elements known at that time in increasing order of atomic masses and this arrangement was periodic table.”

In periodic table:- horizontal line is called periods
vertical line is called group.
Period=7
group=9(I,II,III,IV,V,VI,VII,VIII,ZERO)

6)Modern Periodic law:-
This law was given by Moseley.
Acc. To Moseley the physical and chemical properties of the elements are the periodic of their atomic numbers.
Period=7   
group=18

Modern Periodic table are classified as:-
s , p , d , f block
s block- alkali & alkaline earth metals.

p block- chalcogen , picogens, halogen and inert gases

d block- transition elements

f block- inner transition elements

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