Page 33 - Curriculum Visions Dynamic Book

Caesium see Cesium Calcium (Ca)
Element 20. Calcium is a hard, silvery alkaline earth metal in group 2 in the Periodic Table. It is the fifth most abundant of the chemical elements in the Earth’s crust.
It does not occur as a native metal, but
in compounds, of which calcium carbonate (limestone) is the most common.The element reacts with air, burning with a yellow–red flame to form a white nitride coating. It reacts with water, liberating oxygen.
Discovery
It was first isolated by Sir Humphry Davy in 1808. He produced it by electrolysis of a mixture of lime and mercury oxide.
Technology
As calcium oxide (lime), it goes into
cement and fertiliser (slaked lime,
hydrated calcium oxide, Ca(OH)2).The Romans roasted limestone to produce
lime (CaO) and used it to make the
first cement (calcium oxide reacts with
carbon dioxide in the air and sets as hard calcium carbonate). It was called calx. By
975 calcium sulphate (CaSO4) was used
to set bones and became known as plaster of Paris. It can also be a reducing agent for metals.
Geology
Calcium does not occur as a native element.
It is found as limestone and chalk (CaCO3) and as gypsum (CaSO4) and fluorite (CaF2). Limestone is one of the world’s most common rocks. Because limestone reacts with water and is thereby dissolved, limestones can be
 These huge stalagmites in the Big Room, Carlsbad Caverns, New Mexico, are the result of calcium carbonate precipitation over thousands of years.
Key facts...
Name: calcium
Symbol: Ca
Atomic number: 20
Atomic weight: 40.07
Position in Periodic Table: group 2 (2)
(alkaline earth metal); period 4 State at room temperature: solid Colour: silvery
Density of solid: 1.55 g/cc
Melting point: 842°C
Boiling point: 1,494°C
Origin of name: from the Latin word
calx, meaning lime
Shell pattern of electrons: 2–8–8–2
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