This German periodic table classroom poster, dating to 1885, may be the oldest surviving in the world. (Image credit: University of St. Andrews) ...

In the modern periodic table, elements are in order of atomic number in periods and groups. Electronic structures model how electrons are arranged in atoms. Groups in the periodic table - AQA ...

The periodic table - AQA. Mendeleev made an early periodic table. In the modern periodic table, elements are in order of atomic number in periods and groups.