Cadmium (Cd)

Cadmium (symbol Cd) is the chemical element with atomic number 48: a transition metal, solid at 0 °C, with an atomic mass of 112.41 u. Discovered in 1817 (Friedrich Stromeyer).

Cadmium is a soft metal, a by-product of zinc, long used in rechargeable batteries and in painters' yellow and red pigments. Highly toxic, it builds up in the body for decades. Its use is now strictly regulated, except in some solar panels.

Key facts

Atomic number: 48
Symbol: Cd
French name: Cadmium
Atomic mass: 112.41 u
Molar mass: 112.41 g/mol
Family: Transition metals
Position: period 5, group 12, d-block
State at 0 °C: Solid
Melting point: 321.1 °C
Boiling point: 766.9 °C
Density: 8.65 g/cm³
Electronegativity (Pauling): 1.69
First ionization energy: 868 kJ/mol
Atomic radius: 155 pm
Electron configuration: [Kr] 4d¹⁰ 5s²
Abundance in Earth's crust: 0.15 ppm (66th most abundant element)
Indicative price: 3 $/kg (order of magnitude)
Radioactive: no
Discovery: 1817, Friedrich Stromeyer

Origin of the name

From the Latin cadmia, calamine.

What does cadmium look like?

A shiny, bluish-white metal, so soft it can be cut with a knife. It tarnishes slowly in air.

Where is cadmium found?

About 0.15 ppm of Earth's crust. It almost always accompanies zinc in sphalerite, and its own minerals are rare.

Natural sources

Greenockite
Otavite
Sphalerite (traces)

How is cadmium produced?

It is recovered during zinc refining, at a rate of about 3 kg of cadmium per tonne of zinc. World output is about 25,000 tonnes a year.

Top producers

China
South Korea
Japan
Canada

What is cadmium used for?

Cadmium telluride solar panels.
Nickel-cadmium batteries (now heavily restricted in Europe).
Yellow, orange and red artists' pigments.
Control rods in nuclear reactors (it absorbs neutrons).
Quantum dots in displays (giving way to alternatives).

In everyday life

Tube of “cadmium yellow” paint
Old Ni-Cd rechargeable batteries
Cigarette smoke (a major source of exposure)

Role in living things

No biological role in humans. It accumulates in the kidneys and liver with a half-life of 10 to 30 years. Smokers absorb about twice as much as nonsmokers, because tobacco concentrates it.

Hazards of cadmium

A recognized carcinogen, it damages the kidneys and weakens bones. Breathing cadmium oxide fumes, for example while welding, can be fatal.

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 cadmium

In 1817, German pharmacy inspector Friedrich Stromeyer investigated a zinc carbonate that turned yellow when heated. He found that the color came from an unknown metal, which he named after cadmia, the Latin name for zinc ores.

Did you know?

In Japan, “itai-itai” disease (“it hurts, it hurts”) struck people living along the Jinzū River, whose rice paddies were polluted by a mine: their bones became brittle and painful.
Claude Monet and other Impressionists were among the first to adopt cadmium yellows, brilliant and stable.
The 2023 Nobel Prize in Chemistry honored quantum dots, originally often made of cadmium selenide.

Isotopes of cadmium

Six stable isotopes and two with extremely slow radioactivity, cadmium-113 and cadmium-116. Cadmium-113 gobbles up neutrons with exceptional appetite.

cadmium-106: 1.245% of natural cadmium, stable
cadmium-108: 0.888% of natural cadmium, stable
cadmium-109: radioactive, half-life 1.26 years. X-ray source in handheld metal analyzers.
cadmium-110: 12.47% of natural cadmium, stable
cadmium-111: 12.795% of natural cadmium, stable
cadmium-112: 24.109% of natural cadmium, stable
cadmium-113: 12.227% of natural cadmium, radioactive, half-life 8 × 10¹⁵ years. Absorbs neutrons extremely strongly: hence cadmium control rods.
cadmium-113m: radioactive, half-life 14.1 years
cadmium-114: 28.754% of natural cadmium, stable
cadmium-116: 7.512% of natural cadmium, radioactive, half-life 2.7 × 10¹⁹ years

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), Palladium (Pd), Silver (Ag), 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 12): Zinc (Zn), Mercury (Hg), Copernicium (Cn).