Periodic table

PERIDIC TABLE:

The periodic table is the arrangement of all the elements in a tabular format. it has 118 elements as of 2016. In the table, the chemical elements are arranged in order of atomic number, usually rows, so that elements with similar atomic structure appear in vertical columns. The elements are arranged in the increasing order of their atomic numbers. The periodic table has 18 vertical columns as group number from 1 to 18 and seven horizontal rows as periods. 

As per old sign convention, the 18 vertical columns were grouped into 8 groups and were represented by roman numerals.