Russian scientist mendeleev table

Dmitri Mendeleev‘s periodic table is the forerunner to the modern periodic table. It is a “periodic” table because it groups elements in rows and columns that showcase recurring properties, such as valence, electronegativity, and ionization energy.

Key Points

• Mendeleev’s first periodic table in 1869 included the 63 known elements and spaces for three predicted, undiscovered elements.

  He revised and refined this table multiple times, as new data came to light.

• Dmitri Mendeleev did not invent the first periodic table. Instead, he devised a table that organizes elements by atomic weight and periodic properties and predicts properties of undiscovered elements.
• The key difference between Mendeleev’s table and the modern table is that the modern table orders elements by increasing atomic number.

  To be fair, the proton and atomic number were unknown in Mendeleev’s time and the difference only changes the position of a few elements.

History