What were the criteria used by Mendeleev in creating his his periodic table?

Q.1. An element X (2,8,2) combines separately with NO3 and (SO4)2 -, (PO4)3 - radicals.

State Mendeleev's periodic law?

what is inter-electronic repulsion ?

Why do all the elements of the (a) same group have similar properties, (b) same period have different properties? answer soon

drawback of modern periodic table

Give Limitations of Mendeleevs Classification.

 how does valency vary in a period on going from left to right in modern periodic table?

atomic weights of first 30 elements

which is the most reactive metal and non-metal ? and why ??

Give 2 advantages and disadvantages of Dobernier's triads.

(a) What is meant by periodicity in properties of elements with reference to the periodic table?

(b) Why do all the tendency to gain electrons change as we go from left to right across a period? Why?

among oxygen O^2- ion and magnesium Mg²⁺ ion what has larger sizes and why???????????????

why in the 3rd period there is 8 elements and not 18th elements ? .. Give reason ..