Mendeleev’s periodic table is an arrangement of elements in an increasing atomic mass order in a table form, such that it reflects similarities and trends in the behavior of elements.
Mendeleev initially arranged elements, one below the other in the order of increasing atomic weight. Elements having similar properties are, placed nearby. Elements with similar properties are, found in the same horizontal row. Mendeleev’s original periodic table, published in 1869 is as follows.
Mendeleev’s periodic table can be understood better by reversing the of elements arrangement.
Here elements are, arranged in an increasing order atomic mass, in a horizontal line. This horizontal arrangement of elements is a ‘period’. When an element has high similarity to an earlier element, the new element is, placed just below the earlier element having similar property to start a new period and so on. The period’s one below the other form a ‘column’ (group). Thus, Mendeleev’s periodic table consists of horizontal rows and vertical columns or periods and groups respectively…
If the element is similar but not very much, it is, placed below but slightly away to differentiate it. So, each column will have two sub columns (A and B) such that, elements in the same sub-columns show more resemblance.