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The essentials

Description 

Here is a brief description of calcium.

• Standard state: solid at 298 K
• Colour: silvery white
• Classification: Metallic
• Availability:

This sample is from The Elements Collection, an attractive and safely packaged collection of the 92 naturally occurring elements that is available for sale.

Calcium is a metallic element, fifth in abundance in the earth's crust, of which it forms more than 3%. It is an essential constituent of leaves, bones, teeth, and shells.

The metal is a silvery colour and is rather hard. Chemically it is one of the alkaline earth elements; it readily forms a white coating of nitride in air, reacts with water, burns with a yellow-red flame, forming largely the nitride.

Calcium does not occur free in nature. Calcium is found mostly as limestone, gypsum and fluorite. Stalagmites and stalactites contain calcium carbonate.

Isolation

Calcium metal is readily available commercially and there is no need to make it in the laboratory. Commercially it can be made by the electrolysis of molten calcium chloride, CaCl₂.

cathode: Ca²⁺(l) + 2e^- → Ca anode: Cl^-(l) → ¹/₂Cl₂ (g) + e^-

The calcium chloride is made by the action of hydrochloric acid upon calcium carbonate. Calcium chloride is also a byproduct in the Solway process used to make sodium carbonate.

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Alternatively, and on small scale, calcium can be made through the reduction of CaO with aluminium or of CaCl₂ with sodium metal

6CaO + 2Al→ 3Ca + Ca₃Al₂O₆

CaCl₂ + 2Na→ Ca + 2NaCl

WebElements is the periodic table on the WWW

WebElementsª, the periodic table on the WWW, URL: http://www.webelements.com/
Copyright 1993-2007 Mark Winter [The University of Sheffield and WebElements Ltd, UK]. All rights reserved.
Document served: Friday 9th May, 2008