Cadmium
Atomic Data
| Atomic Number | 48 |
| Symbol | Cd |
| Atomic Weight | 112.41 u |
| Density (STP) | 8.65 g/cm³ |
| Melting Point | 321.07 °C (594.22 K) |
| Boiling Point | 766.85 °C (1040 K) |
| Electronegativity | 1.69 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 |
| Oxidation States | +2 |
| Phase at STP | Solid |
| Category | Transition Metal |
| Period / Group | 5 / 12 |
| CAS Number | 7440-43-9 |
Electron Configuration
[Kr] 4d10 5s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| O | 5 | 5s | 2 | 48 |
| Total | 48 | 48 | ||
Isotopes of Cadmium
Cadmium has eight naturally occurring stable isotopes. The most abundant is ¹¹⁴Cd, comprising 28.73% of all naturally occurring Cadmium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Cadmium-106 | ¹⁰⁶Cd | 48 | 58 | 1.25 | Stable |
| Cadmium-108 | ¹⁰⁸Cd | 48 | 60 | 0.89 | Stable |
| Cadmium-110 | ¹¹⁰Cd | 48 | 62 | 12.49 | Stable |
| Cadmium-111 | ¹¹¹Cd | 48 | 63 | 12.8 | Stable |
| Cadmium-112 | ¹¹²Cd | 48 | 64 | 24.13 | Stable |
| Cadmium-113 | ¹¹³Cd | 48 | 65 | 12.22 | Stable |
| Cadmium-114 | ¹¹⁴Cd | 48 | 66 | 28.73 | Stable |
| Cadmium-116 | ¹¹⁶Cd | 48 | 68 | 7.49 | Stable |
Abundance & Occurrence
Cadmium is present in Earth's crust at approximately 0.15 ppm by mass and at approximately 2 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Acute systemic toxicity: Cadmium and its compounds are acutely toxic by inhalation and ingestion; inhaling cadmium oxide fumes causes acute chemical pneumonitis that can be fatal; the TLV for cadmium fume is 0.01 mg/m3.
- Carcinogenicity: Cadmium and cadmium compounds are Group 1 human carcinogens (IARC); occupational inhalation exposure is associated with lung cancer; cadmium is also classified as nephrotoxic and a reproductive toxicant.
- Itai-itai disease: Environmental cadmium contamination in Japan's Jinzu River caused itai-itai ('it hurts, it hurts') disease: a combination of painful osteoporosis and kidney failure from chronic dietary cadmium exposure.
- Nickel-cadmium batteries: Spent NiCd batteries must not be incinerated or landfilled; cadmium leaching from improper disposal is a significant environmental and groundwater contamination concern.
- Regulatory status: Cadmium is restricted in many consumer products under RoHS and REACH; verify compliance before any industrial or consumer application involving cadmium compounds.
Cadmium in the Real World
Real-World Uses
- Nickel-cadmium (NiCd) batteries: Cadmium is the anode material in NiCd rechargeable batteries, which provide high discharge currents and long cycle life used in power tools, emergency lighting, medical equipment, and aircraft starting systems.
- Cadmium telluride solar cells: CdTe thin-film photovoltaic modules are one of the most cost-effective large-scale solar technologies, with First Solar manufacturing gigawatts annually; CdTe has a near-ideal band gap for solar energy conversion.
- Electroplating for corrosion protection: Cadmium electroplating provides excellent corrosion protection in marine and aerospace environments, low contact resistance, and good lubricity on steel aircraft fasteners and military hardware.
- Pigments: Cadmium yellow (CdS) and cadmium red (CdSe/CdS) are heat-stable, chemically inert pigments with brilliant, saturated colours; used in artists' paints, high-temperature plastics, and ceramic glazes.
- Nuclear reactor control: Cadmium has an extremely high thermal neutron capture cross-section; cadmium-silver-indium control rods absorb neutrons in pressurised water reactors to regulate the fission rate.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is cadmium used for?
Cadmium's largest use was in nickel-cadmium (NiCd) rechargeable batteries, which are being replaced by nickel-metal hydride and lithium-ion types due to cadmium's toxicity. Cadmium sulphide and cadmium selenide are used as vivid yellow, orange, and red pigments in artists' paints and plastics. Cadmium telluride is used in some thin-film solar cells. Cadmium is also used as a neutron absorber in nuclear reactor control rods.
Is cadmium toxic?
Cadmium is highly toxic and a known human carcinogen. It accumulates in the kidneys and liver over a lifetime, causing kidney damage even at low long-term exposures. Cadmium causes itai-itai disease, a painful condition first identified in Japan after rice paddies were contaminated by mining effluent: the name means 'it hurts, it hurts' in Japanese. Occupational exposure from cadmium dust and fumes must be strictly controlled.
How was cadmium discovered?
Cadmium was discovered in 1817 by German chemist Friedrich Stromeyer, who found a new oxide as an impurity in zinc carbonate (calamine). When he heated the impure calamine, it turned yellow rather than white, indicating a contaminant. He isolated the new metal and named it cadmium after Kadmeia, the ancient Greek name for calamine. The element was discovered independently the same year by Karl Hermann.
What is itai-itai disease?
Itai-itai disease is a form of cadmium poisoning first documented in Toyama Prefecture, Japan, in the 1950s and 1960s. Cadmium-contaminated wastewater from a mining operation upstream was used to irrigate rice paddies, and the local population ingested cadmium-contaminated rice over many years. Cadmium accumulated in their kidneys and caused tubular kidney disease and severe osteoporosis. Sufferers experienced excruciating pain with each movement, which gave the disease its name.