Mendeleev claimed the famous periodic law that “Element properties are a periodic function of their atomic weight.” Mendeleev placed elements in the order of their atomic weights in the form of a table known as the Periodic Table of Mendeleev.
Characteristics of Mendeleev’s periodic table:
- In Mendeleev periodic table, vertical columns in the periodic table and horizontal row in the periodic table were named as groups and period respectively.
- The periodic table is composed of seven horizontal rows or periods and is numbered between 1 to 7.
- There is a regular gradation in the properties of elements in the horizontal rows(periods) from left to right.
- The periodic table is composed of eight vertical columns or groups. They are numbered between 1 to 8.
- If the element is similar but not much, to distinguish between them, it is placed below and slightly away from it. Thus, each column will have two sub-columns A and B, so elements will show more similarity in the same sub-columns.
- 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 into two subgroups, 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