Periodic table

Some key features: 

1.In 1869 first attempt was made by Dmitri Mendeleev . He arranged element in accordance with increasing order of atomic number.

2. After that Dobereiner comes he tell us the tried rule . i.e. group of 3 elements.the mean of atmoic weight is same.

3. In 1904 , Richard abegg formulated Abegg's rule. This rule was used later on 1916 by Gilbert N. Lewis & formulated as octat rule.

4.octat rule is the properties of 8th element are similar with 1st element.

5.Modern periodic table is given by Mendeelv.  Modern periodic law states that " physical & chemical properties of element are periodic function of their atomic number "

 periodic table the element are arranged in accordance with their increasing atomic number

6. There are 7 periods & 18 groups . Which are divided into three blocks s,p,d&f 

7.In groups the element are arranged in accordance with their last valance electron.

8. Elements are come in exist when BIG-BANG  is happens.

some data :

1. Out of 118 elements 92 are naturally occurring  ( expection technetium &promethium are occur due to nuclear activities  ).

2.  Metals - 91

      Non - metals -17

Transition -38

Metalloids - 11. 


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Link:  https://en.wikipedia.org/wiki/Periodic_table?wprov=sfla1