Cadmium (Cd), atomic number 48, is a soft, silvery-white metal that sits in group 12 of the periodic table alongside zinc and mercury, and it shares traits with both despite being chemically distinct.

Cadmium is not considered a true transition metal by many chemists because its common oxidation state does not involve partially filled d or f electron shells.

It was discovered in 1817 independently by Friedrich Stromeyer and Karl Samuel Leberecht Hermann in Germany, both while studying impurities in zinc compounds.

The element’s name comes from “calamine,” a zinc ore, which itself traces back to the ancient name Cadmea, linked to Greek mythology.

Cadmium is extremely rare in Earth’s crust, with an average concentration of only about 0.1 to 0.5 parts per million.

Despite its rarity, cadmium is widely distributed because it naturally occurs as an impurity in zinc ores like sphalerite.

Most cadmium is not mined directly but instead produced as a byproduct during zinc, lead, and copper refining.

Pure cadmium metal is soft enough to be cut with a knife and can be bent easily due to its low hardness.

At room temperature, cadmium has a hexagonal close-packed crystal structure, which influences its physical strength and malleability.

Cadmium melts at about 321°C, which is unusually low compared to many other transition metals.

The metal boils at around 767°C, making its liquid range relatively narrow compared to many other metals.

Cadmium has a density of about 8.65 g/cm³, making it significantly heavier than zinc but lighter than mercury.

One of cadmium’s key chemical behaviors is that it almost always forms +2 oxidation state compounds.

It can also exist in unusual +1 states under special chemical conditions, though these are far less common.

Cadmium burns in air to form cadmium oxide, a compound that can appear brown or dark red depending on its crystalline form.

Cadmium compounds dissolve in strong acids like hydrochloric acid, sulfuric acid, and nitric acid, forming corresponding cadmium salts.

Naturally occurring cadmium consists of several isotopes, many of which are stable, including Cd-110, Cd-111, and Cd-112.

Because of its neutron-absorbing ability, cadmium is used as a “neutron poison” to help regulate nuclear fission reactions.

Nickel cadmium (Ni Cd) batteries once dominated portable power storage before lithium ion batteries became widespread.

Cadmium sulfide is a key yellow pigment used in paints and plastics due to its brightness and durability.