In 1869 the great Russian scientist Dmitri Mendeleyev announced the discovery of the Periodic Law of elements. So science received the key to the secrets of matter. All the greatest discoveries which have been made since then in the fields of chemistry and physics have been based on this law. The elements in Mendeleyev’s Periodic Table follow one another in the order of their atomic weights. They are arranged in periods and groups. Mendeleyev’s discovery made it possible for the scientists to find 38 new chemical elements to fill the empty spaces left in the Periodic Table. At the same time they tried to find elements heavier than the last element in the Periodic Table. In 1955 the American scientist Dr. Glenn Seabord obtained element № 101 and named it Mendelevium in honour of the creator of the Periodic Law.