Period 6 element
A period 6 element is one of the chemical elements in the sixth row (or period) of the periodic table of the 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 with similar behaviour fall into the same vertical columns. The sixth period contains 32 elements, tied for the most with period 7, beginning with caesium and ending with radon. Lead is currently the last stable element; all subsequent elements are radioactive, however bismuth has a half-life of more than 1019 years, more than 1,000 times longer than the current age of the universe. As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order, however there are exceptions, such as cerium.
[edit] Properties
This period contains the lanthanides, also known as the rare earths. Many lanthanides are known for their magnetic properties, such as neodymium. Many period 6 transition metals are very valuable, such as gold, however many period 6 poor metals are incredibly toxic, such as thallium. Period 6 contains the last stable element, lead. All subsequent elements in the periodic table are radioactive. After bismuth, which has a half-life or more than 1019 years, polonium, astatine, and radon are some of the shortest-lived and rarest elements known; astatine is currently the rarest natural element, with less than a gram estimated to exist on earth at any given time[1]
[edit] Characteristics
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Chemical element Chemical series Electron configuration 55 Cs Caesium Alkali metal [Xe] 6s1 56 Ba Barium Alkaline earth metal [Xe] 6s2 57 La Lanthanum Lanthanide[a] [Xe] 5d1 6s2 [b] 58 Ce Cerium Lanthanide [Xe] 4f1 5d1 6s2 [b] 59 Pr Praseodymium Lanthanide [Xe] 4f3 6s2 60 Nd Neodymium Lanthanide [Xe] 4f4 6s2 61 Pm Promethium Lanthanide [Xe] 4f5 6s2 62 Sm Samarium Lanthanide [Xe] 4f6 6s2 63 Eu Europium Lanthanide [Xe] 4f7 6s2 64 Gd Gadolinium Lanthanide [Xe] 4f7 5d1 6s2 [b] 65 Tb Terbium Lanthanide [Xe] 4f9 6s2 66 Dy Dysprosium Lanthanide [Xe] 4f10 6s2 67 Ho Holmium Lanthanide [Xe] 4f11 6s2 68 Er Erbium Lanthanide [Xe] 4f12 6s2 69 Tm Thulium Lanthanide [Xe] 4f13 6s2 70 Yb Ytterbium Lanthanide [Xe] 4f14 6s2 71 Lu Lutetium Lanthanide [a] [Xe] 4f14 5d1 6s2 72 Hf Hafnium Transition metal [Xe] 4f14 5d2 6s2 73 Ta Tantalum Transition metal [Xe] 4f14 5d3 6s2 74 W Tungsten Transition metal [Xe] 4f14 5d4 6s2 75 Re Rhenium Transition metal [Xe] 4f14 5d5 6s2 76 Os Osmium Transition metal [Xe] 4f14 5d6 6s2 77 Ir Iridium Transition metal [Xe] 4f14 5d7 6s2 78 Pt Platinum Transition metal [Xe] 4f14 5d9 6s1 [b] 79 Au Gold Transition metal [Xe] 4f14 5d10 6s1 [b] 80 Hg Mercury Transition metal [Xe] 4f14 5d10 6s2 81 Tl Thallium Poor metal [Xe] 4f14 5d10 6s2 6p1 82 Pb Lead Poor metal [Xe] 4f14 5d10 6s2 6p2 83 Bi Bismuth Poor metal [Xe] 4f14 5d10 6s2 6p3 84 Po Polonium Metalloid [Xe] 4f14 5d10 6s2 6p4 85 At Astatine Halogen [Xe] 4f14 5d10 6s2 6p5 86 Rn Radon Noble gas [Xe] 4f14 5d10 6s2 6p6
- a Note that lutetium (or, alternatively, lanthanum) is considered to be a transition metal, but marked as a lanthanide, as it is considered so by IUPAC.
- b An exception to the Aufbau principle.
[edit] References
- ^ Gray, Theodore (2009). The Elements: A Visual Exploration of Every Known Atom in the Universe. New York: Black Dog & Leventhal Publishers. ISBN 978-1-57912-814-2.
Element categories in the periodic table
| Metals | Metalloids | Nonmetals | Unknown chemical properties |
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| Alkali metals |
Alkaline earth metals |
Inner transition metals | Transition metals |
Post-transition metals |
Other non-metals |
Halogens | Noble gases |
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| Lanthanides | Actinides | |||||||||
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