Question

sulpur is placed in group 6a ,chlorine in a group 7a argon in a group 18 of the periodic table . give reason for it . give me answer don't give me link

Answer 1

Sulphur is placed in group-16, Chlorine is placed in group-17 and Argon is placed in group-18 in long-form of periodic table.
In Mendeleev periodic table there is no space for noble gases like Argon. And it placed Sulphur in group-6A and Chlorine in 7A.
So we can not give the reason for 6A 7A and 18 at same time.

In long form of periodic table the elements are arranged according to increasing order of their atomic number. Hence there is a place for each elements even for noble gases like argon. Argon is placed in group-18 as there is no sub group and group numbers are from 1 to 18 according to the electronic configuration of electron in an atom.
But Mandeleev periodic table was based on reaction of element to form oxides and hydrides hence there is no place for noble gases like Argon. More over verticle rows were divided into sub groups because of difference in properties that is why S and Cl got the position in sub group-6A and & 7A as their properties match with sub group-A