The periodic table is a chart or a tabular arrangement of chemical elements that are ordered by their atomic number, properties and electron configuration. The periodic table was founded by Russian chemist Dmitri Mendeleev, which first published the same in 1869. The row of the table is called as periods, the columns as groups. The ordering generally indicates the periodic trends, such as elements with similar behavior in the same column. The table also shows elements with similar chemical properties. The elements on the left are metal and the ones on the right are non-metals. The gaps in the table were left intentionally to fill unknown elements.