Periodic table

The periodic table is an ordered arrangement of chemical elements in rows called periods and columns called groups. It depicts the periodic law, in which properties approximately recur when elements are ordered by atomic number. The table has four blocks, and elements in the same group tend to have similar chemical characteristics. Dmitri Mendeleev's 1869 table was the first generally accepted version. A recognisably modern form was reached in 1945.

Organization

Rows called periods and columns called groups

Generally accepted table

Dmitri Mendeleev, 1869

Modern form

Reached in 1945