Write two points on which classification of elements were based in Mendeleev's periodic table *
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Answer:
Explanation of Mendeleev’s Periodic Table:
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.