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Lanthanum is a chemical element with the symbol La and the atomic number 57. It is a soft , ductile , silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table , of which lanthanum is the first and the prototype.
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, [12] 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.
A period 6 element is one of the chemical elements in the sixth row (or period) of the periodic table of the chemical elements, including the lanthanides.The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements ...
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
A table listing the 17 rare-earth elements, their atomic number and symbol, the etymology of their names, and their main uses (see also Applications of lanthanides) is provided here. Some of the rare-earth elements are named after the scientists who discovered them, or elucidated their elemental properties, and some after the geographical ...
Lavoisier writes the first modern list of chemical elements – containing 33 elements including light and heat but omitting Na, K (he was unsure of whether soda and potash without carbonic acid, i.e. Na 2 O and K 2 O, are simple substances or compounds like NH 3), [89] Te; some elements were listed in the table as unextracted "radicals" (Cl, F ...
However, the first element to be discovered by synthesis rather than in nature was technetium in 1937.) The row was completed with the synthesis of tennessine in 2010 [76] (the last element oganesson had already been made in 2002), [77] and the last elements in this seventh row were given names in 2016. [78]
Alchemical symbols for the modern elements Symbol Element Atomic number Notes Phosphorus: 15 (discovered late) 🜍 Sulfur: 16: used by Newton Manganese: 25: late; used by Torbern Bergman (1775) ♂: Iron: 26: classical planetary metal of Mars 🜶 Cobalt: 27: late; used by Bergman Nickel: 28