Question No.  6631 :
Who invented the periodic table?

Dmitri Ivanovich Mendeleev (1834-1907) was born in Siberia as the youngest of 17 children. Mendeleev catalogued thousands of facts about the 63 elements known at the time. He became convinced that groups of elements had similar, "periodic" properties. He arranged the known elements according to their increasing atomic mass, leaving blank spaces where he was sure other, unknown elements would fit. He was so bold as to predict the properties of these unknown elements based on the idea of periodic properties. Because of his work, today he is considered to be the Father of the Periodic Table. Mendeleev's periodic charts contained no atomic numbers, as our modern periodic charts do, because the atomic structure of elements was not yet known. Where Mendeleev ordered elements by atomic mass, modern periodic charts order elements by atomic number, which is the number of protons contained in the nucleus of the atom of an element. The order of atomic mass and the order of atomic number, however, turn out to be almost the same. Since atomic masses were not in all cases accurately known, Mendeleev did not hesitate to make some corrections in the order. As a consequence of the arrangement he became aware of apparent gaps in the known elements. It was the prediction that not only would two new elements be found with atomic masses between zinc and arsenic (the elements we know as gallium and germanium) but that their properties were predicted as well that is the mark of his genius. The properties of gallium predicted by Mendeleev in 1869 match well its actual properties measured after its discovery in 1875. Since none of the noble gas elements were then known, Mendeleev could not and did not predict them. With this exception, and the actual discovery of some of the less-common elements and the lanthanide and actinide groups, our modern periodic chart is the same as that produced by Mendeleev. A similar arrangement was devised at about the same time by the German chemist Julius Lothar Mayer, but Mayer did not venture to predict new or missing elements. Although Dmitri Mendeleev is often considered the "father" of the periodic table, the work of many scientists contributed to its present form. Dmitri Mendeleev came up with the first version of the periodic table in 1864. Since then more than 700 versions of the table have been proposed. Question Asked By:

Name: Sophia Xiong

Age Group: 13 to 20

Occupation Type: Student

Education Level: Primary