Periodic Table: Historic perspective

• Dmitri Mendeleev (1834–1907) developed the modern periodic table.
• Argued that element properties are periodic functions of their atomic weights

• Periodic law
• When the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically.
• Elements having similar physical and chemical properties fall within a column.
• We now know that element properties are periodic functions of their atomic numbers.