Dmitri+Mendeleev(DD)


 * __Dmitri Mendeleev__**

date of birth: February 8th 1834 date of death: February 2nd 1907 country of origin: Russia · Born in Verhnie Aremzyani village as the youngest of many children. · Began work on spectroscope and published several titles about the subject. · Became Director of the Bureau of Weights and Measures · As a teacher he attempted to classify elements by properties and led to the making of the first periodic table. · Proposed a table of know element (of the time) and some undiscovered ones. He stated 1. The elements, if arranged according to their atomic weight, exhibit an apparent periodicity of properties. 2. Elements which are similar in regards to their chemical properties have atomic weights which are either of nearly the same value e.g., Ir,Os) or which increase regularly (e.g., K, Rb, Cs 3. Arrangements of the elements in groups of elements in the order of their atomic weights corresponds to their so-called valencies, as well as, to some extent, to their distinctive chemical properties; as is apparent among other series in that of Li, Be, B, C, N, O, and F 4. The elements which are the most widely diffused have small atomic weights 5. The magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body 6. We must expect the discovery of many yet unknown elements–for example, two elements, analogous to aluminium and silicon, whose atomic weights would be between 65 and 75 7. The atomic weight of an element may sometimes be amended by a knowledge of those of its contiguous elements. Thus the atomic weight of tellurium must lie between 123 and 126, and cannot be 128. Here Mendeleev was wrong as the atomic mass of tellurium (127.6) remains higher than that of iodine (126.9)Certain characteristic properties of elements can be foretold from their atomic weight. [|(http://en.wikipedia.org/wiki/Dmitri_Mendeleev] . Unknown author also stated on nobelprize.org) · Made other contributions like Proposed lighter atomic element than hydrogen, Created formula for expansion of gas, Given credit for metric system introduction · Has Mendelevium named after him along with a moon crater and several honors
 * 1869, he arranged elements in 7 different groups with similar properties, known as the first version of periodic table