Calcium is an alkaline earth metal represented by the symbol Ca and atomic number 20 on the Periodic Table. It is the fifth most abundant element found in the Earth’s crust, constituting approximately 3.64% of its mass. This element is widely recognized for its importance in biological systems, being the most plentiful inorganic element in the human body. Calcium is a fundamental component of various everyday materials, from the structure of mountains to the plaster used in construction.
Calcium’s State of Matter Under Normal Conditions
At the standard conditions typically encountered in daily life, Calcium exists as a solid. Standard temperature and pressure (STP) defines these normal conditions, which generally corresponds to a room temperature of about 25 degrees Celsius (77 degrees Fahrenheit). The atoms of elemental Calcium are organized into a dense, repeating structure known as a face-centered cubic crystal lattice. This ordered arrangement is characteristic of metals and is held together by strong metallic bonds, which tightly anchor the individual calcium atoms in place, preventing them from moving freely past one another.
The Temperatures Required for Phase Change
Changing the state of elemental Calcium from a solid requires the input of a significant amount of thermal energy to overcome the strong metallic bonds holding the crystal structure together. Calcium’s melting point is approximately 842 degrees Celsius (1,548 degrees Fahrenheit), a temperature far exceeding that of a standard oven or kiln. Once this temperature is reached, the metal transitions into a liquid state. To change the state again, from liquid to gas, even more energy is needed, as Calcium’s boiling point is extremely high, occurring at about 1,484 degrees Celsius (2,703 degrees Fahrenheit). These intense thermal requirements explain why Calcium remains a stable solid under nearly all natural conditions on Earth.
Essential Properties of Elemental Calcium
Pure, elemental Calcium is a moderately soft, silvery-white metal that can be cut with a knife, though it is harder than metals like lead. This element is chemically reactive, particularly with air and water. When exposed to the atmosphere, the shiny metal rapidly tarnishes, developing a dull, grayish-white coating. This coating is a surface layer of calcium oxide and calcium nitride, which forms as the metal reacts with oxygen and nitrogen in the air. Elemental Calcium also has a relatively low density of about 1.55 grams per cubic centimeter, making it a lightweight metal.
Where We Find Calcium and Its Common Uses
Due to its high chemical reactivity, Calcium is never found in nature in its pure, elemental form. Instead, it exists bound with other elements in various compounds that are widely distributed across the planet. The most common of these compounds is calcium carbonate (CaCO3), which is the main component of limestone, marble, chalk, and the shells of marine organisms. In the construction industry, calcium compounds are fundamental, such as in the creation of cement and plaster, and calcium sulfate is processed into plaster of Paris and drywall. Biologically, calcium phosphate is the primary inorganic constituent that provides structural rigidity to bones and teeth in animals and humans.