The Organizational Skills of Mendeleev

Although the evolution of the modern Periodic Table of Elements had many major contributions a Russian chemist Dmitri Mendeleev is credited with first trying to organize the chemical elements according to atomic weights  in 1869. He had predicted that the properties of the elements would change as the atomic weight increased. However Mendeleev discovered that these gradual changes changed suddenly at distinct steps or periods. Thus he grouped the elements in a table with both rows and columns. Mendeleev's discoveries led to the modern periodic table which we use today and is organized by atomic number.

The Periodic Table of Elements

The rows in a periodic table are called periods, and as you move right along a given period the chemical properties of the elements gradually change. The period number signifies the highest energy level an electron in that element occupies. The columns in the periodic table are called groups, and the elements in a given group share similar chemical and physical properties. a group of elements have identical valence electron configurations which allows them to behave in similar chemical fashion.