Question

the modern periodic table has been evolved through the early attempt of dobereiner,Newland and Mandeleev. list advantage and disadvantage of all the three attempts

Answer 1

dobereiner traits ecetion is his law vaild only for lither elements

Answer 2

marit of doberenar is traid rule and demarit is it is not 4 all drawback of new is it is not valid after calcium and mand is position of isotope