Palladium, along with platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). platinum group metals share similar chemical properties, but palladium has the lowest melting point and is the least dense of these precious metals.
The unique properties of palladium and other platinum group metals account for their widespread use. Palladium is found in many electronics including, multi-layer ceramic capacitors, component plating and low voltage electrical contacts. Palladium is also used in dentistry, medicine, hydrogen purification, chemical applications, and groundwater treatment. Palladium plays a key role in the technology used for fuel cells, which combines hydrogen and oxygen to produce electricity, heat and water.
Palladium has a very atypical configuration in its outermost electron shells Palladium is a soft silver-white metal that resembles platinum. It is the least dense and has the lowest melting point of the platinum group metals. It is soft and ductile when annealed and greatly increases its strength and hardness when it is cold-worked. Palladium dissolves slowly in sulphuric, nitric, and hydrochloric acid. This metal also does not react with oxygen at normal temperatures (and thus does not tarnish in air). Palladium heated to 800°C will produce a layer of palladium(II) oxide (PdO). It lightly tarnishes in moist atmosphere containing sulphur.
The metal has the uncommon ability to absorb up to 900 times its own volume of hydrogen at room temperatures. It is thought that this possibly forms palladium hydride (PdH2) but it is not yet clear if this is a true chemical compound. When palladium has absorbed large amounts of hydrogen, it will expand slightly in size.
Common oxidation states of palladium are 0,+1, +2 and +4. Although originally +3 was thought of as one of the fundamental oxidation states of palladium, there is no evidence for palladium occurring in the +3 oxidation state; this has been investigated via X-ray diffraction for a number of compounds, indicating a dimer of palladium(II) and palladium(IV) instead. Recently, compounds with an oxidation state of +6 were synthesised.
The base value of each unit of ranges between 2 and 20Ð per unit, with up to 3 units being found at any one time.
Presence on Mars: Rare
|Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6|
|Group 2|||Argon | Bromine | Cadmium | Gallium | Germanium | Gold | Helium III | Krypton | Molybdenum | Neon | Niobium | Nitrogen | |Palladium | Rhodium | Rubidium | Ruthenium | Scandium | Selenium | Silver | Strontium | Technetium | Titanium | Vanadium | |Yttrium | Zirconium||