Periodic Classi...

For which element, the Law of Octaves was not found to be applicable?

 In Mendeleev's Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later?

Doberiener's system of classification into triads was not found to be useful as he could identify only:

Which one of the following does not increase while moving down the group of the periodic table?

The correct order of increasing radius of the elements Si, Al, Na and P is:

In the Modern Periodic Table, the metals among the first ten elements are

The correct sequence of atomic radii is 

Based on general trends in the periodic table, predict which element in each of the following pairs has the most metallic character.
(i) Sn or Pb    (ii) Ag or Sr    (iii) Al or B    (iv) Br or As

Arrange the following elements in the order of their increasing non-metallic character:

Which of the following accounts best for the fact that fluorine atom is smaller than that of oxygen?