Mendeléev’s periodic table consists of how many periods
 

Concept: Mendeleev’s periodic law states that when the elements are arranged in the increasing order of their atomic masses , the elements with similar properties recur at regular intervals.

There are seven periods (numbered from 1 to 7) or horizontal rows in the Mendeleev’s periodic table. The periods 4, 5 and 6 are divided into two halves. 

The first half of the elements are placed in the upper left corners and the second half occupy lower right corners in each box