Periodic Classi...

In Mendeleev table, the triad of VIII group is :

An element which is an essential constituent of all organic compounds belongs to :

Arrange the following elements in the order of their decreasing metallic character.
$$Na,\ Si,\ Cl,\ Mg,\ Al$$

The total number of inert gases among the following is:

Mendeleev predicted the existence of certain elements not known at that time and named as Eka-aluminiumT he elements which have taken the place of Eka-aluminium is :

The period of element with atomic number 20  in the periodic table is :

The group number of element with atomic number 7 in the periodic table is:

Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order?

The three elements A, B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. Such an arrangement of elements called as :

According to Dobereiner's triads, the atomic mass of the 2nd element is equal to the __________ of 1st and 3rd elements in that triad.