Question

describe Mendeleev's periodic law?

Answer 1

Elements are arranged in the periodic table in the increasing order of their relative atomic masses.Mendeleev divided his periodic table in eight groups and seven periods.Groups from I to VII are meant for normal elements and group VIII is for transition elements.Groups from I to VII have been divided in two sub groups, while group VIII is meant for three elements.Periods from 4th to 7th have been divided in two series: 1st series and 2nd series.Elements having similar properties have been kept in the same group. For example; lithium, potassium, rubidium, etc. are in 1st group.

Two general formulae; one for oxides and second for hydrides; have been given for the elements of each group in the periodic table. For example: R2O for oxides and RH for hydrides, of the elements; of 1st group.

Using the given general formulae; the formula of oxides and hydrides can be written for the elements of each group. For example; hydrogen, sodium, potassium, etc. belong to the first group. The general formula of oxides for the elements of 1st group is R2O. Accordingly they form H2O, Na2O, K2O, etc.

Answer 2

Mendeleev's Law states that:
The physical and chemical properties of elements are a periodic function of their atomic weights i.e. when the elements are arranged in order of their increasing atomic weight, elements with similar properties are repeated after certain regular intervals. This repetition of properties of elements after certain regular intervals is called periodicity of properties.