Platinum group elements - Platinum group elements

The six elements Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Osmium (Os), Iridium (Ir), and Platinum (Pt) are collectively called the platinum group elements because they have similar properties. In the 18-group periodic table, they are in groups 8, 9, and 10. Because their properties are similar, they occur together in nature as alloys. They are representative precious metals and are resistant to acid, alkali, and oxygen. They also have high melting and boiling points. Os and other elements can take an octavalent state, which, combined with their large ionic radius, forms eight-coordinate compounds. Since their electronegativity is about 2.2, most compounds are covalent. They are used as catalysts in many chemical reactions. The most important one is the three-way catalyst for purifying automobile exhaust gas, in which Pt, Rh, and Pd are used. Pt is also used as an electrode material for fuel cells. Because they are chemically stable, platinum is used in chemical crucibles and evaporating dishes, for example.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

ルテニウムRu，ロジウムRh，パラジウムPd，オスミウムOs，イリジウムIr，白金Ptの6元素は，性質が似ているので白金族元素と総称される．18族型周期表では8，9，10族になる．性質が似ているので天然には合金として一緒に産出する．代表的な貴金属で，酸，アルカリ，酸素などに侵されにくい．融点，沸点も高い．Osなどは八価の状態もとり，イオン半径の大きいことと相まって八配位の化合物をつくる．電気陰性度は2.2程度であるため，多くの化合物は共有結合性である．多くの化学反応に触媒として用いられる．とくに重要なものは自動車排気ガス浄化用三元触媒でPt，Rh，Pdが使われる．Ptは燃料電池電極材としても使われる．化学的に安定なので，たとえば白金などは化学用るつぼ，蒸発皿などに利用されている．

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