Periodic table part 2

Periodic table   part-2

(E): Telluric Helix :

A three dimensional periodic table given by De-chan-chortois.  This table is also known as tellurix helix. 

(F): Mendeleev's periodic table:

1. Mendeleev's periodic law - The physical and chemical properties of element are the periodic function of their atomic wt.
2. It is based on atomic weight.
3. 63 element was known noble gases were not discovered.
4. He was the first scientist to classify the elements in a systematic manner that is in horizontal row and in vertical columns.
5. Horizontal rows are called periods and there was 7 periods in Mendeleev periodic table
6. Vertical columns are called groups and there were eight groups in Mendeleev periodic table.
7. Each group of 28 is divided into a and b subgroups a Sub group elements are called Normal elements and B Sub group elements are called transition elements.
8. The metal belonging to the same group exhibit similar properties. 

Demerits of Mendeleev's periodic table:

• Position of hydrogen -  Hydrogen resembles both, the alkali metals and halogens in properties so Mendeleev could not decide where to place it.
• Position of isotopes - As atomic weight of isotopes differ ,they should have placed in different positions.In Mendeleev's periodic table, but there were no such place for isotopes in Mendeleev's periodic table. 
• Anomalous pair of element- There were some pair of element which did not follow the increase order of atomic weight.