All practice pages/Interatomic theory/Elements
Element 48, a transition metal
A soft metal behind brilliant yellow and red paints and rechargeable batteries, and a toxic one behind a mass poisoning in Japan.
Period 5, group 12. The other transition metals are tinted, and every cell opens its own article.
Cadmium has 48 electrons, one for every proton, so the atom carries no charge. Below are the same 48 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s²
Short form: [Kr] 4d¹⁰ 5s², where [Kr] stands for the 36 electrons krypton already has.
That list runs by shell. In the order the subshells fill it reads [Kr] 5s² 4d¹⁰, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 3 here is 3s² 3p⁶ 3d¹⁰, and 2 + 6 + 10 is 18.
Cadmium sits in period 5 and has 5 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones cadmium can lose, gain or share, so they are the ones that decide what it bonds with.
Cadmium gives up its two 5s electrons to form Cd²⁺, its only common ion, much like zinc above it.
No ores are mined for cadmium alone. It occurs in zinc ores, especially sphalerite, and is recovered during zinc refining.
Friedrich Stromeyer found it in 1817 while investigating zinc carbonate that turned yellow when heated. The name comes from the Latin cadmia, an old name for zinc carbonate ore.
Nickel-cadmium rechargeable batteries used most of it, though they are being phased out. Cadmium telluride makes thin-film solar panels, cadmium pigments give artists' paints brilliant yellows, oranges and reds, and cadmium absorbs neutrons in some reactor control rods.
Toxic, and a cause of cancer. Cadmium from mining waste in the Jinzū River basin of Japan caused itai-itai disease in the 20th century, which softened bones and caused severe pain.