Palladium (Pd)

Palladium (symbol Pd) is the chemical element with atomic number 46: a transition metal, solid at 0 °C, with an atomic mass of 106.42 u. Discovered in 1803 (William Hyde Wollaston).

Palladium is a precious metal of the platinum family, lighter and cheaper than platinum. It can soak up to 900 times its own volume of hydrogen, like a sponge. It is found mainly in the catalytic converters of gasoline cars and in the capacitors of electronic devices.

Key facts

Atomic number: 46
Symbol: Pd
French name: Palladium
Atomic mass: 106.42 u
Molar mass: 106.42 g/mol
Family: Transition metals
Position: period 5, group 10, d-block
State at 0 °C: Solid
Melting point: 1,554.9 °C
Boiling point: 2,962.9 °C
Density: 12.02 g/cm³
Electronegativity (Pauling): 2.2
First ionization energy: 804 kJ/mol
Atomic radius: 140 pm
Electron configuration: [Kr] 4d¹⁰
Abundance in Earth's crust: 0.015 ppm (70th most abundant element)
Indicative price: 50,000 $/kg (order of magnitude)
Radioactive: no
Discovery: 1803, William Hyde Wollaston

Origin of the name

From the asteroid Pallas, discovered shortly before.

What does palladium look like?

A shiny, malleable, silvery-white metal that does not tarnish in air.

Where is palladium found?

Rare, about 0.015 ppm of Earth's crust. It is concentrated in nickel-copper deposits (Norilsk in Siberia, Sudbury in Canada) and platinum deposits (the Bushveld in South Africa).

Natural sources

Braggite
Stibiopalladinite
Potarite
Nickel-copper ores (Norilsk)

How is palladium produced?

It is obtained as a by-product of nickel and platinum, then purified chemically. World mine output is close to 200 tonnes a year; Russia (Norilsk Nickel) supplies about 40%.

Top producers

Russia
South Africa
Canada
United States
Zimbabwe

What is palladium used for?

Catalytic converters for gasoline cars (about 80% of demand).
Multilayer ceramic capacitors in electronics.
Dental alloys.
White gold and jewelry.
Catalysts for drug synthesis and hydrogen purification.

In everyday life

Car catalytic converter
Smartphone circuit boards
White-gold ring
Metal dental crown

Role in living things

No biological role. It can cause contact allergies, especially in people sensitive to nickel.

Hazards of palladium

Low toxicity as a metal. Finely divided and loaded with hydrogen, it can ignite solvents, so chemists handle it with care.

Cosmic origin

Dying stars: Made slowly in red giants (stars like the Sun at the end of their lives).
Neutron stars: Created when two neutron stars collide — the “forge” of gold.

History of palladium

In 1802–1803, William Hyde Wollaston isolated palladium from crude platinum and named it after the asteroid Pallas, discovered a year earlier. Instead of publishing, he put it up for sale anonymously in a London shop. The chemist Richard Chenevix then claimed it was a fake, an alloy of platinum and mercury; Wollaston only revealed the truth in 1805.

Did you know?

Wollaston anonymously offered a reward to anyone who could make artificial palladium: nobody claimed it, and for good reason.
The “cold fusion” announced in 1989 by Fleischmann and Pons relied on palladium electrodes loaded with deuterium; it was never confirmed.
The 2010 Nobel Prize in Chemistry honored palladium-catalyzed reactions, used to make drugs and OLED screens.

Isotopes of palladium

Six stable isotopes. Palladium-103 is slipped into the prostate as tiny seeds to treat cancer.

palladium-102: 1.02% of natural palladium, stable
palladium-103: radioactive, half-life 17 days. Implanted seeds for prostate cancer brachytherapy.
palladium-104: 11.14% of natural palladium, stable
palladium-105: 22.33% of natural palladium, stable
palladium-106: 27.33% of natural palladium, stable
palladium-107: radioactive, half-life 6.5 × 10⁶ years. Long-lived fission product; its extinct traces date meteorites.
palladium-108: 26.46% of natural palladium, stable
palladium-110: 11.72% of natural palladium, stable

Related elements

Same family (transition metals): Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Yttrium (Y), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Technetium (Tc), Ruthenium (Ru), Rhodium (Rh), Silver (Ag), Cadmium (Cd), Hafnium (Hf), Tantalum (Ta), Tungsten (W), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt), Gold (Au), Mercury (Hg), Rutherfordium (Rf), Dubnium (Db), Seaborgium (Sg), Bohrium (Bh), Hassium (Hs).

Same column (group 10): Nickel (Ni), Platinum (Pt), Darmstadtium (Ds).