Cadmium
Definition and meaning of Cadmium in chemistry.
![Cadmium element card: symbol Cd, atomic number 48, atomic mass 112.41, electron configuration [Kr] 4d¹⁰ 5s², oxidation states +2, Transition metal, group 12, period 5, solid at room temperature.](/assets/images/terms/cadmium-chemical-element.webp)
Cadmium is a soft, bluish-white transition metal with the symbol Cd and atomic number 48. This toxic heavy metal shares many of its chemical properties with zinc. Industrial companies usually obtain cadmium as a secondary byproduct when they refine zinc ores.
In more detail
Cadmium sits in group 12 of the periodic table, directly below zinc. It has a low melting point and resists chemical corrosion very well. The metal almost always shows a stable oxidation state of +2 in its compounds.
This single state is unusual because most transition metals show many different states. Cadmium is highly toxic to living things and causes serious environmental problems. It accumulates in the kidneys and liver, where it can cause permanent organ damage.
A common student misconception is that cadmium behaves like a typical reactive metal. However, it is relatively stable in dry air and does not react easily with water. Manufacturers use cadmium to coat steel because it acts as a protective barrier.
This coating is especially useful in salty marine environments where iron rusts quickly. Due to its toxicity, many countries now restrict its use in consumer goods. It is also used to make yellow pigments for artist paints. This bright compound is called cadmium sulfide and is chemically very stable.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Cd |
| Atomic number | 48 |
| Atomic mass | 112.41 u |
| Category | Transition-Metal |
| State at room temperature | Solid |
| Melting point | 321.07 degrees Celsius |
Cadmium was once a key component in nickel-cadmium rechargeable batteries. These batteries powered portable tools and electronics because they could be recharged many times. The battery functions by moving electrons back and forth between nickel and cadmium electrodes. However, disposing of these old batteries created heavy metal pollution in landfills. Rainwater dissolved the toxic cadmium, which then leaked into local drinking water supplies. Because of these serious health risks, manufacturers now replace them with lithium-ion batteries. This change shows how green chemistry replaces toxic materials with safer alternatives that protect the environment.
Frequently asked questions
Why is cadmium use so heavily regulated?
Cadmium is a highly toxic carcinogen that builds up in the body over time. It can damage kidneys and bones if it enters food or water.
Where does industrial cadmium come from?
Mining companies do not mine cadmium directly from the earth. Instead, they extract it as a byproduct when refining zinc ores.
Why does cadmium resist rusting so well?
It forms a thin oxide layer in air that blocks oxygen from reaching the metal underneath. This layer prevents further chemical reactions.
Related terms
Sources & references
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