Periodic table
Russian chemistry professor Dmitri Mendeleev and German chemist Julius Lothar Meyer independently published their periodic tables in 1869 and 1870, respectively. Mendeleev's table was his first published version; that of Meyer was an expanded version of his (Meyer's) table of 1864. They both constructed their tables by listing the elements in rows or columns in order of atomic weight and starting a new row or column when the characteristics of the elements began to repeat.
Periodic trends
Discovery of Periodic Law constitutes one of the most singularly important events in the history of chemical science. Almost every chemist makes extensive and continued use of Periodic Law. Periodic Law also led to the development of the periodic table, which is widely used nowadays.