The periodic table is also referred to as the periodic table of elements. The periodic table is a displayed in a tabular form of chemical elements, the elements being arranged in an increasing order of their atomic number, chemical properties and electron configuration. The structure of the table tends to show the periodic trends. The seven rows which are present in the word count are known as periods. The elements present on the left are generally called the metals, and the elements on the right are generally the non-metals. The columns on the other hand are referred to as groups, which has elements having similar chemical behaviors. The six groups have accepted names along with assigned group numbers. For example, group 17 are commonly called the halogens and group 18 being the noble gases.

The way of organization of the periodic table can be used to derive the relation between the properties of various elements, and also to predict the chemical properties and behaviors of the undiscovered or the newly synthesized elements. The first ever recognizable periodic table was developed by the Russian chemist Dmitri Mendeleev, in the year of 1869. He had also made assumptions regarding the few unidentified elements that were expected to fill in the gaps within the periodic table. Among the assumptions, most of them had come out to be correct.  Mendeleev’s idea about the slow expansion and the refined discovery of the synthesis elements and the development of the new theories explained the chemical behavior of the elements present in the periodic table. The modern day periodic table in the recent times provides a useful framework for the analysis of the chemical reactions and continues to have a wide usage in the field of chemistry, other form of sciences and nuclear physics.

The elements starting from atomic number 1 to 118 have been brought into existence providing completion of the full seven rows of the periodic table. The first 94 elements which are present there on the periodic table are occurring naturally. Out of these 94 elements, some are found in traces and some were discovered only in nature after having been synthesized first. The elements ranging from 95 to 118 have been synthesized in laboratories or nuclear reactors. After the discoveries, the periodic table took a halt at 118, as a reason of which, new synthesis of newer elements are under process. After the discovery of new elements, these will be placed in a separate group forming a different 8^th group. Theoretical studies have led to discoveries of new elements which might turn out to be probable candidates to be placed into the periodic table. Various synthetic radionuclides of elements which occur naturally have also been discovered into laboratories.

Within the periodic table, each chemical element possesses a unique atomic number (Z) representing the present number of protons in its nucleus. Most of the elements in the table have varying numbers of neutrons and the other forms of the same elements are generally known as isotopes.