The 59 elements that make up Groups 1B through 8B of the periodic table are called transition metals. They form four series. The elements of the first series begin the transition from metals to nonmetals, the elements of the second and third series continue the transition, and the elements of the fourth finish it. These elements are transitional because of the way their electrons are distributed within the atom.
In Groups 1A through 7A, called “representative” elements, the number of electrons in the outer shell (valence electrons) increases as the atomic number increases. But in the transition metals, Groups IB—8B, the number of electrons in the outer shell does not reflect the increase in atomic number—there are never more than two. Instead, it is the number of electrons in the next-inner shell that increases.
First series: Scandium through zinc
Scandium is a soft, silvery-white metal, used mainly in high-intensity lights.
Scandium was one of the “missing” elements predicted by Dimitri Medeleev. It was discovered in 1879 by the Swedish chemist Lars Nil-son (1840-1899). He named it after Scandia, the Latin name for Scandinavia. Its atomic number is 21, and its atomic mass is 44.9559. Its melting point is 1539° C, and its boiling point, 2832° C.
Second series: Yttrium through cadmium
Yttrium is a heavy, silvery-white metal that resembles the elements of the group called the lanthanides. It is used in electronics, especially lasers, and in ceramics, chemicals, and glass.
Yttrium is one of several elements named after the town of Ytterby in Sweden. It was discovered by the Swedish chemist Carl Gustav Mosander (1797-1858) in 1843 in the mineral yttria. Its atomic number is 39, and its atomic mass is 88.9059. Its melting point is 1522±8° C, and its boiling point, 3338° C.
Third series I: Lanthanum and the rare earths
Lanthanum, a soft, pliable silvery-white metal, is used in making lighter flints and as a catalyst in the glass industry.
Lathanum was discovered in 1839 as an impurity in cerium by Carl Mosander. Its name derives from the Greek lanthano, which means to be hidden. Its atomic number is 57, and its atomic mass is 138.906. Its melting point is about 920° C, and its boiling point, about 3469° C.
Third series II: Hafnium through mercury
Hafnium, a silver-colored metal, absorbs neutrons so efficiently that it is used to control the rate of fission reaction in nuclear power plants.
Hafnium was discovered in 1923 by theDutch physicist Dirk Coster (1889-1950) and the Hungarian chemist Georg von Hevesy (1885-1966). Hafnium is derived from Hafnia, the Latin name for Copenhagen (Denmark), where the element was discovered. Its atomic number is 72, and its atomic mass is 178.49. Its melting point is 2227° C, and its boiling point, 4602° C.
Fourth series: Actinium through lawrencium
The elements from actinium to lawrencium, known as the actinides, form an offshoot of Group 3B of the periodic table. These highly radioactive elements have many physical and chemical properties in common.
Actinium was discovered in 1899 by the French scientist Andre Debierne. Its name is derived from the Greek aktis, meaning a ray of light. Its atomic number is 89, and its atomic mass is 227.028. Its melting point is 817° C, and its boiling point, 2470° C.
Reamde more Transition metals
Comments
Post a Comment