Palladium (Pd): Properties, Uses, Health & Environmental Effects

Overview

Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal in appearance.  In the periodic table, palladium is located in group 10, period 5, d-block.  The periodic table is a chart that shows how chemical elements are related to each other. Palladium, ruthenium, rhodium, Osmium, indium and platinum makes up the platinum group of metals. Due to the nature of their reactivity, these metals can also be referred to as noble metals. They are generally less reactive. These metals have similar properties, but palladium has the lowest melting point and is the least dense of them.

What You Need To Know About Palladium

Discovery

Palladium was discovered along with rhodium in 1803 by English Chemist William Hyde Wollaston (1766-1828). Wollaston had been studying platinum ores, taken from South America. The name Palladium was taken from Pallas, an asteroid that had been discovered at about the same time.

Occurrence In Nature

Palladium occurs in nature as a free metal and also alloyed with gold, platinum and other platinum group metals. The metal is mined primarily in Russia and South Africa and mostly extracted as a secondary product from operations that are focused on other metals such as platinum or nickel. It is also extracted as a by-product of copper and zinc refining.  Palladium is also found in United States and Canada.

Periodic Table Facts

• The atomic symbol of Palladium on the periodic table of elements is Pd.
• In the periodic table, palladium is located in group 10, period 5, d-block. 
• Palladium is categorized as a transition metal in the periodic table.
• The atomic number of palladium is 46. Atomic number is the number of protons.
• The ground state electronic configuration of neutral tungsten is [Kr]4d¹⁰.
• Electrons per shell in Palladium are 2, 8, 18, 18.

Physical Properties

• Palladium is a hard, silver-white metal that resembles platinum.
• Palladium is malleable and ductile. Malleable means, capable of being hammered into thin sheets whereas ductile means capable of being drawn into thin wires.
• Palladium has an extensive ability to absorb hydrogen (up to 900 times its own volume).
• Palladium is a solid at standard temperature and pressure.
• Palladium metal that is paramagnetic at room temperature.
• Palladium is soft and ductile when annealed and is greatly increased in strength and hardness when cold-worked.
• The melting point of palladium is 1828.05K (2830.82^oF, 1554.9^oC).
• Boiling point of palladium is 2963^oC (3236K, 5365^oF).
• Density of palladium is 12.023 grams per cubic centimeter (g/cm³).
• The heat of fusion of palladium is 16.74 kJ/mol
• The heat of vaporization of palladium is 358 kJ/mol
• Palladium has a Molar heat capacity of 25.98 kJ/(mol.K).

Extraction

• Palladium occurs in nature as a free metal and also alloyed with gold, platinum and other group metals.
• Palladium is removed from platinum ores after platinum and gold have been removed. The metal is converted to palladium chloride (PdCl₂) and then purified as pure palladium.
• Commercially, palladium is produced from nickel-copper ore deposits where it is found in small quantities.

Other properties

• Palladium is one of the six platinum group metals consisting of platinum, palladium, rhodium, osmium, iridium and ruthenium.
• There are six naturally occurring isotopes of palladium that is, palladium-102, palladium-105, palladium-106, palladium-108 and palladium-110.
• The electrical resistivity and thermal conductivity of palladium is 105.4nΩ.m (at 20^oC) and 71.8 W/ (m.k).
• The atomic weight of palladium is 106.42. Atomic weight is the average mass of the atom.
• The electronegativity of palladium according to the Pauling scale is 2.20.
• The first, second and third Ionization energies of palladium is 804.4 kJ/mol, 1870 kJ/mol and 3177 kJ/mol respectively.
• Palladium has an Atomic radius of 137pm.
• Palladium has a face-centered cubic crystalline structure at ordinary temperatures.
• The Vander Waals radius of palladium is 163 pm.

Reactions

• Palladium does not react with oxygen at standard temperature (it does not get tarnished by atmosphere).
• Palladium is more reactive than the other platinum metals. For example it is attacked more readily by acids than any of the other platinum metals.
• Palladium dissolves slowly in concentrated nitric acid, in hot concentrated sulfuric acid and when finely ground, in hydrochloric acid.
• Palladium also dissolves readily at room temperature in aqua regia.
• Compounds of palladium primarily exist in the 0 and +2 oxidation state. Other less common states are also recognized. Generally the compounds of palladium are more similar to those of platinum than those of any other element.
• Palladium combines with fluorine and chlorine when very hot.

Uses Of Palladium  

• Palladium is commonly alloyed with gold, silver and copper. The alloys are used in a variety of products.
• It is used more in electrical appliances such as wide screen televisions, computers and mobile phones in the form of tiny multi-layered ceramic capacitors.
• It is used in making watch bearings and in making of blood sugar test strips.
• Finely divided palladium is a good catalyst and is used to speed up hydrogenation and dehydrogenation reactions.
• Palladium is also used as a catalyst in breaking down petroleum (cracking process) to make high quality gasoline and other products.
• Palladium is used to purify hydrogen, this is because hydrogen easily diffuses through heated palladium and this provides a way of separating and purifying the gas.
• Palladium is used in making aircraft spark plugs, surgical instruments and electrical contacts.
• It is used in dental fillings.
• Palladium metal and its alloys serve as substitutes for platinum in jewelry and in electrical contacts.
• Palladium salts are used in electroplating.
• Palladium is used in making springs, balance wheels and mirrors in scientific instruments.
• Palladium together with rhodium is mostly used in automobile catalytic converters; the palladium serves as a catalyst to convert polluting hydrocarbons, carbon monoxide and nitrogen oxide in the exhaust to water, carbon dioxide and nitrogen.
• Palladium electrodeposits or coatings are used in printed-circuit components.
• Palladium is used in crowns.
• Palladium an excellent electrocatalyst for oxidation of primary alcohols in alkaline media.
• Palladium sometimes alloyed with nickel is used for component and connector plating in consumer electronics and in soldering materials.
• Palladium is used in the platinotype printing process to make fine-art black-and-white prints.

Health & Environmental Effects

• Palladium is non-toxic has no known biological role in humans or plants.
• There is no known evidence of serious health or environmental effect of exposure to palladium or its compounds.

Summary Of The Properties Of Palladium In Tabular Form