Page 32 - Curriculum Visions Dynamic Book

C see Carbon; Ca see Calcium Cadmium (Cd)
Element 48. Cadmium is a silvery- white metal in the zinc group (transition metals) in the Periodic Table. Cadmium is a soft metal, easily cut with a knife. It has a low melting point. One unique feature is the way the metal makes a sound like a scream when it is bent.
Discovery
Friedrich Stromeyer, a German chemist, discovered the element in 1817 by extracting cadmium sulphide from an ore containing mostly zinc carbonate.
Technology
Cadmium is obtained as a by-product during the refining of zinc ores. It is used in Ni–Cd (nicad) batteries and for electroplating steel, iron, copper, brass and in other alloys to protect them from corrosion. Silver solder is made
with cadmium. It goes into some of the phosphors that coat television tubes. Because it absorbs neutrons, cadmium also makes control rods in nuclear reactors. Cadmium compounds also go into pigments. Because cadmium is a very toxic heavy metal, its application is now more restricted.
Geology
Found as small amounts as impurities in zinc ores such as sphalerite (zinc sulphide, ZnS) and smithsonite (zinc carbonate, ZnCO3).
Biology
Highly toxic heavy metal.
 Cadmium is a dense metal that is used to shield nuclear reactors and as the moderating material for the control rods inside the reactor core.
Key facts...
Name: cadmium
Symbol: Cd
Atomic number: 48
Atomic weight: 112.4
Position in Periodic Table: transition metal,
group (12) (zinc group); period 5 State at room temperature: solid Colour: silvery-white
Density of solid: 8.65 g/cc
Melting point: 321°C
Boiling point: 765°C
Origin of name: from the Greek word kadmeia,
meaning calamine (because cadmium was first found as an impurity in a mineral once called calamine, zinc carbonate. Calamine is now known as smithsonite).
Shell pattern of electrons: 2–8–18–18–2
For more on cadmium, see Volume 6: Zinc, Cadmium and Mercury in the Elements set.
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