Periodic Classification of Elements - INDIA COVER

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Periodic Classification of Elements

Periodic Classification of Elements 

How many Elements are Presently in periodic Table :
At present, there are 118 elements, are known to us.

How many Naturals elements present ?
There are 94 naturally occurring elements in modern periodic table

"Doberneirs Traids"

Year : 1817 ( Germany )
Name : Johann Wolfgang Doberneir
Work : Tried to arrange the similar properties into groups

Doberiner showed that when the three element in a triad were written in the order of increasing  "atomic masses"

Atomic mass of the middle element was roughly the average of atomic masses of other two elements

Example :


Cl + I = 35.5 + 127 
= 162.5 / 2
= 80 (approx)

Discovered :
First observed the platform as a catalyst and discovered similar triads of element

"Newlands Law of Octaves"

Year : 1866 ( English Scientist )
Name : John Newlands
Work : Arranged the known elements in the increasing order of atomic masses from hydrogen to thorium

Hydrogen is the 1st element and the thorium is the last element of the table

Totally 56 elements , 

  • Compared to the Octaves found in the music called law of Octaves
  • He found every eighth element have the same properties similar to the first element
  • Sodium and Lithium similar each other
  • Worked well with lighter elements only
  • Applicable only up to calcium every eighth element did not posses properties similar to the first

"Mendeleev periodic table"

Year : 1869 ( Russia )
Name : Dmitri Mendeleev
Work : He arranged the elements on the basis of
  • Fundamental property
  • Atomic mass
  • Similarity of Chemical Properties
  • Mendeleev started the work with 63 elements, were known at the time.
  • He examined relationship between the atomic masses of the elements and their physical and chemical properties
  • Concentrated on Hydrogen and Oxygen
  • increasing order of atomic masses
D Mendeleev periodic law Statement :
 The properties of elements are the periodic function of their atomic masses " contains vertical columns called groups and horizontal rows are called periods .

"Henry Moseley law"

Year : 1913
Name : Henry Moseley
Work: Showed that the atomic number ( symbolized as Z ) of an element is more fundamental property than its atomic masses

Henry Moseley law Statement : 
" The properties of an element are a periodic function of their atomic number " elements are arranged in the order of increasing atomic number.

Modern Periodic table has 18 Vertical Columns known as "groups" and 7 horizontal rows known as "periods".

Important Ques :

1, Who is the father of modern periodic table arranged on the basis of atomic masses - Dmitri Mendeleev

2, Who is the father of modern periodic table arranged on the basis of atomic number - Henry Mosley ( RRB junior Engineer Ques 2019 )

3, Who is called as law of Octaves ? - Newlands

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