Page 51 - Curriculum Visions Dynamic Book

Platinum (Pt)
Element 78. Platinum is a soft, easily worked, and very heavy silvery- white metal. It is one of the transition metals in the Periodic Table.
Platinum has a high melting point and corrodes only very slowly in air, although it corrodes in the presence of alkalis. It is barely soluble in concentrated acids unless they are mixed together (as aqua regia). It is regarded as a precious metal. Platinum, like palladium, absorbs large volumes of hydrogen. It is also used as an agent to speed up chemical reactions (a catalyst). Hydrogen and oxygen gas mixtures explode in the presence of platinum wire. Platinum is a catalyst in the catalytic converters used in car exhausts.
Discovery
It was discovered by Julius Caesar Scaliger in 1557.
Technology
Platinum expands at the same rate as glassware, and so it is used to make electrodes for chemical apparatus. It also goes into jewellery and dental devices. Platinum anodes
are used to protect ships, pipelines, and steel piers from salt water corrosion.
Geology
Platinum is found as a native metal in deposits near ancient volcanoes. It also occurs as platiniridium, a naturally occurring platinum–iridium alloy. It also occurs in sulphide ores as platinum sulphide, PtS.
Biology
Platinum is not found in living things.
Platinum electrodes are used for electrolysis in the laboratory because they are resistant to corrosion.
Key facts...
Name: platinum
Symbol: Pt
Atomic number: 78
Atomic weight: 195.08
Position in Periodic Table: transition metal, group
(10), (nickel group); period 6. Precious metal State at room temperature: solid
Colour: silvery-white
Density of solid: 21.45 g/cc
Melting point: 1,768.3°C
Boiling point: 3,825°C
Origin of name: the Spaniards found it in the river
deposits of the Río Pinto, Colombia, and they named it platina del Pinto because it looked like silver.
Shell pattern of electrons: 2–8–18–32–17–1
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