group on the periodic table definition chemistry

GROUP ON THE PERIODIC TABLE DEFINITION CHEMISTRY SERIES

However, these elements are neither rare in abundance nor 'earths' (an obsolete term for water-insoluble strongly basic oxides of electropositive metals incapable of being smelted into metal using late 18th century technology). The 'earth' in the name 'rare earths' arises from the minerals from which they were isolated, which were uncommon oxide-type minerals.

Together with the stable elements of group 3, scandium, yttrium, and lutetium, the trivial name ' rare earths' is sometimes used to describe all the lanthanides.

GROUP ON THE PERIODIC TABLE DEFINITION CHEMISTRY SERIES

The term derives from lanthanum, first discovered in 1838, at that time a so-called new rare-earth element 'lying hidden' or 'escaping notice' in a cerium mineral, and it is an irony that lanthanum was later identified as the first in an entire series of chemically similar elements and gave its name to the whole series. Rather than referring to their natural abundance, the word reflects their property of 'hiding' behind each other in minerals. Despite their abundance, the technical term 'lanthanides' is interpreted to reflect a sense of elusiveness on the part of these elements, as it comes from the Greek λανθανειν ( lanthanein), 'to lie hidden'. The term 'lanthanide' was introduced by Victor Goldschmidt in 1925. Primordial From decay Synthetic Border shows natural occurrence of the element Etymology

However, owing to widespread current use, lanthanide is still allowed. The 1985 IUPAC 'Red Book' (p. 45) recommends using lanthanoid instead of lanthanide, as the ending -ide normally indicates a negative ion. This convention is entirely a matter of aesthetics and formatting practicality a rarely used wide-formatted periodic table inserts the 4f and 5f series in their proper places, as parts of the table's sixth and seventh rows (periods), respectively. In presentations of the periodic table, the f-block elements are customarily shown as two additional rows below the main body of the table. Since 'lanthanide' means 'like lanthanum', it has been argued that lanthanum cannot logically be a lanthanide, but the International Union of Pure and Applied Chemistry (IUPAC) acknowledges its inclusion based on common usage. These elements are called lanthanides because the elements in the series are chemically similar to lanthanum.

All lanthanide elements form trivalent cations, Ln 3+, whose chemistry is largely determined by the ionic radius, which decreases steadily from lanthanum (La) to lutetium (Lu). The term rare-earth element or rare-earth metal is often used to include the stable group 3 elements Sc, Y, and Lu in addition to the 4f elements. Lutetium is a d-block element (thus also a transition metal), and on this basis its inclusion has been questioned however, like its congeners scandium and yttrium in group 3, it behaves similarly to the other 14. All but one of the lanthanides are f-block elements, corresponding to the filling of the 4f electron shell. The informal chemical symbol Ln is used in general discussions of lanthanide chemistry to refer to any lanthanide. Lutetium (element 71) is also sometimes considered a lanthanide, despite being a d-block element and a transition metal. In the periodic table, they fill the 4f orbitals. The lanthanide ( / ˈ l æ n θ ə n aɪ d/) or lanthanoid ( / ˈ l æ n θ ə n ɔɪ d/) series of chemical elements comprises at least the 14 metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium.

Group on the periodic table definition chemistry