Cd · Element 48 · Transition metal
A soft, toxic metal that gave the world rechargeable NiCd cells and the brilliant yellow of old paint.
Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where cadmium sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Same element, different neutrons
All cadmium atoms have the same number of protons, 48, and differ only in their number of neutrons: those variants are its isotopes. The most common, Cd-114, has 66 neutrons and makes up 28.754% of natural cadmium.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Cd-106 | 58 | 1.245% | Stable | — |
| Cd-108 | 60 | 0.888% | Stable | — |
| Cd-110 | 62 | 12.470% | Stable | — |
| Cd-111 | 63 | 12.795% | Stable | — |
| Cd-112 | 64 | 24.109% | Stable | — |
| Cd-113 | 65 | 12.227% | 8.04 × 10¹⁵ yrs | β⁻ |
| Cd-114 most common | 66 | 28.754% | Stable | — |
| Cd-116 | 68 | 7.512% | 3.3 × 10¹⁹ yrs | 2β⁻ |
The classroom shortcut, rounded atomic mass minus atomic number, gives 64 for cadmium, but the most common cadmium atom has 66 neutrons: the atomic mass, 112.414, is an average over all natural isotopes.
Decay modes
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Size, to scale
Radius 151 pm — that is 0.151 nm, so about 3.31 million of them side by side would span a millimetre.
Thermal range
Cadmium is liquid over a 446 K window, from 594 K to 1040 K.
The story
Cadmium (Cd) is element 48, a soft, bluish-white metal in group 12, below zinc and above mercury. It melts at 321 °C (594.22 K), boils at 767 °C (1,040 K) and has a density of 8.65 g/cm³. Cadmium and its compounds are toxic and are classed as human carcinogens, which has led to strict limits on its use.
Cadmium has 48 electrons in five shells, arranged 2, 8, 18, 18, 2, with the configuration [Kr] 4d¹⁰ 5s². Like zinc, it almost always forms the Cd²⁺ ion.
Natural cadmium contains eight isotopes; the most abundant is cadmium-114, at about 29%. Cadmium-113 absorbs slow neutrons very strongly, which is why cadmium is used to control nuclear reactions. Two of the natural isotopes, cadmium-113 and cadmium-116, are radioactive, with half-lives far longer than the age of the universe.
In 1817 Friedrich Stromeyer, a professor at Göttingen who also inspected pharmacies, investigated samples of zinc carbonate that turned yellow when heated even though they contained no iron. He traced the color to a new metal and named it cadmium, from the Latin cadmia, the old name for zinc carbonate ore (calamine).
In the same year Karl Samuel Leberecht Hermann found the element independently in zinc oxide from Silesia, and both men are credited with its discovery.
Cadmium found little use until the late 19th century, when cadmium sulfide became a popular yellow pigment. Its use grew in the 20th century in plating, batteries and plastics, until its toxicity, made clear by itai-itai disease in Japan, led to restrictions from the 1970s onward.
Applications
Nickel-cadmium (NiCd) rechargeable batteries have long been the largest use of cadmium. They are robust and work well in the cold, and they are still used in aircraft, railway and backup power systems. The European Union has banned them from most portable devices, where lithium-ion and nickel-metal hydride batteries have replaced them.
Cadmium telluride (CdTe) is the leading thin-film solar cell material and is used in large solar farms.
Because of its toxicity, the EU RoHS directive limits cadmium in electrical and electronic equipment to 0.01% by weight, and many countries restrict it in plastics, jewelry and toys.
Cadmium is less common at home than it once was. You may still find it in older NiCd rechargeable batteries and cordless tools, in cadmium-based artists' paints, in some colored ceramics and glass, and in cadmium telluride solar panels. It also reaches people through food and tobacco: cigarette smoke is one of the main sources of cadmium exposure for smokers.
Where it comes from
0.15 mg/kg of Earth's crust · more abundant than 43% of elements
Cadmium is rare, at about 0.15 parts per million of Earth's crust. Its only notable mineral, greenockite (cadmium sulfide), is uncommon and is not mined on its own.
Cadmium is chemically similar to zinc and replaces it in zinc ores, especially sphalerite (zinc sulfide). Almost all cadmium is recovered as a byproduct of zinc refining, so its supply follows zinc production. China, South Korea, Japan and Canada are among the leading refiners (USGS).
Cadmium enters soils and water from zinc mining and smelting, phosphate fertilizers and waste. Plants such as rice, leafy vegetables and tobacco take it up from soil, which is how it enters the food chain.
Handling
Cadmium and its compounds are toxic. The International Agency for Research on Cancer classifies them as carcinogenic to humans (Group 1), mainly causing lung cancer. Breathing cadmium oxide fumes, produced when cadmium-plated or cadmium-containing metal is heated, welded or cut, can cause severe and sometimes fatal lung damage that may begin hours after exposure.
Cadmium builds up in the kidneys and stays in the body for decades. Long-term exposure damages the kidneys and weakens bones. In Japan's Jinzū River basin, cadmium from a zinc mine contaminated rice fields and caused itai-itai disease, a painful bone disease that was officially recognized as pollution-related in 1968.
Quick answers
Cadmium (symbol Cd) is element 48 on the periodic table, a transition metal in period 5, group 12. A soft, toxic metal that gave the world rechargeable NiCd cells and the brilliant yellow of old paint. At room temperature it is a solid.
[Kr] 4d¹⁰ 5s², giving 5 occupied shells with the distribution 2, 8, 18, 18, 2.Cadmium melts at 594.2 K (321.1 °C) and boils at 1040 K (766.9 °C).
The standard atomic weight of cadmium is 112.414 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.
The most common cadmium atom, Cd-114, has 66 neutrons: its mass number, 114, minus its atomic number, 48. It makes up 28.754% of natural cadmium. The classroom shortcut, rounded atomic mass (112.414) minus atomic number, gives 64 instead, because the atomic mass is an average over all natural isotopes of cadmium.
Cadmium has a density of 8.65 g/cm³. Water is 1.0 g/cm³, so a block of cadmium is about 8.7× heavier.
Cadmium has a Pauling electronegativity of 1.69. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Cadmium was discovered in 1817 by Stromeyer & Hermann. Origin of the name: Latin cadmia, "calamine".
Cadmium makes up about 0.15 mg/kg of the Earth's crust — genuinely rare, which is why it is expensive.