Mendeleev & The Periodic Table

Mendeleev for a Day Activity

Mendeleev’s Table Organized elements by increasing atomic mass so that elements with similar properties were in the same column.

Mendeleev’s Prediction After Mendeleev placed all the known elements in his periodic table, several empty spaces were left. In 1871 Mendeleev predicted the existence and properties of elements that would fill three of the spaces. By 1886, all three of these elements had been discovered.

Mendeleev’s Prediction Predicted Eka-aluminum in 1871 Soft metal Low melting point Density of 5.9 g/cm3 Found: Gallium in 1875 Melting Point 29.7 C Density of 5.91 g/cm3

Mendeleev’s Predictions

Usefulness of His Table The close match between Mendeleev’s prediction and the actual properties of new elements showed how useful his periodic table could be.

Henry Moseley (1913, British) Organized elements by increasing atomic number. Fixed problems in Mendeleev’s arrangement.