The Element Calcium
Calcium (Ca) is a chemical element with atomic number 20. It plays significant roles in various biological systems and is an abundant element in the Earth’s crust.
Classification and General Appearance
Metal, Non-metal, or Metalloid?
Calcium is classified as a metal. More specifically, it belongs to the group of alkaline earth metals, found in Group 2 of the periodic table. This classification indicates its metallic characteristics, including conductivity and electron-donating tendencies in chemical reactions.
Color and Luster
When freshly cut or pure, calcium exhibits a silvery-white color and possesses a bright metallic luster. However, it reacts readily with oxygen and moisture in the air. This rapid reaction causes the surface to tarnish, forming a dull, grayish-white oxide layer that obscures its initial shine. This tarnishing process is observable in various environments globally where calcium compounds are exposed to the atmosphere.
Physical State and Mechanical Properties
State at Room Temperature
At standard room temperature (approximately 20-25 °C), calcium exists as a solid.
Texture and Malleability
Calcium is a relatively soft metal. It is soft enough to be cut with a knife under appropriate conditions. Like many metals, it exhibits malleability, meaning it can be hammered into thin sheets, and ductility, allowing it to be drawn into wires. However, its high reactivity means that pure, workable forms are typically not encountered in common applications outside specialized laboratory or industrial settings. For instance, calcium’s presence in common building materials like concrete (derived from calcium carbonate found in limestone) contributes to their structural integrity worldwide, from the Great Pyramids of Giza to modern skyscrapers.
Thermal Properties
Melting Point
The melting point of calcium is approximately 842 °C. This temperature is relatively high for a metal of its type, indicating strong metallic bonding.
Boiling Point
Calcium transitions from a liquid to a gaseous state at its boiling point, which is approximately 1484 °C.