Cadmium is a soft, bluish-white metal with atomic number 48 that exhibits key chemical properties: low melting point (321°C), high toxicity, and tendency to form divalent compounds. These traits make it valuable in industrial applications while posing significant environmental hazards.
Cadmium shares group 12 of the periodic table with zinc and mercury, inheriting some similar characteristics but with distinct differences. Unlike mercury, cadmium doesn't form metallic bonds easily, which limits its use in electrical applications compared to its group neighbors.
The metal resists corrosion and oxidation in dry air but forms a protective oxide layer when exposed to humid conditions. This passive layer prevents further reaction, making cadmium useful in plating applications where corrosion resistance matters.
| Property | Value/Characteristic |
|---|---|
| Atomic mass | 112.41 g/mol |
| Electronegativity (Pauling scale) | 1.69 |
| Common oxidation state | +2 |
| Reactivity with acids | Dissolves in dilute sulfuric acid, releasing hydrogen gas |
| Toxicity | Highly toxic to humans and ecosystems |
Primary sources of cadmium include zinc ores, where it appears as a byproduct during zinc refining. The metal's low melting point and ability to absorb vibrations make it ideal for:
When working with cadmium, proper ventilation and protective equipment are critical. The metal's toxicity becomes apparent through bioaccumulation in organisms, particularly in aquatic environments where it binds to organic matter.
One non-obvious fact: cadmium's toxicity increases when combined with other elements. For example, cadmium telluride solar panels require careful handling due to elevated toxicity levels compared to pure cadmium.
In my work with industrial coatings, I observed cadmium plating on steel components used in marine environments. The protective oxide layer formed on exposure to saltwater prevented corrosion far better than zinc coatings. However, strict regulations now limit this application due to environmental concerns about cadmium runoff.