periodic table part 1

Periodic table  Part.1

(A) Prouts concept 

Is simply asm.com the elements are made up of hydrogen so we can say that  ..

Atomic weight of element= n×(Atomic weight.of one hydrogen atom)

Where n= no. of hydrogen atom= 123

Drawbacks or limitations:

Letter on elements discovered having atomic weight infections like chlorine atomic weight 35.5, Strontium atomic weight 87.5 and proud could not explain why this weights are instructions beasar this is a drawback.

(B). Dobereiner trait rule

1. He made groups of three elements having similar chemical properties 
2. In Dobereiner trait, atomic weight of middle element is equal to the average atomic weight of first and third element.

Eg.   Cl               Br.            I

         35.5           80.0.         127

       

         35.5+127/2 =  81.25

(C) Newland law of octaves

1. He arrange the element in increasing order of their atomic mass and observe that properties of every 8th element was similar to the first one like in the case of musical vowels notation.                 Sa  re  ga  ma  pa  dha. ne. Sa.         1.   2.    3.    4.    5.    6.    7.     8.
2. At that time inert gases was not known.
3. The properties of alkali are similar to eight element that is    na, b are similar to MG and so on.              

Drawback or limitations:

• This rule is valid upto CA . Because after CA due to the presence of D block element there is difference of 18 elements instead of 8 element.
• After the discovery of inert gas and included in the periodic table it becomes the eighth element from alkali metal so the sla had to be dropped out.
• He failed in the case of heavy metals as fe been placed atoms with O and S