Calcium is a metallic element that has the atomic number 20. Some of its most important chemical properties are that it has 10 isotopes, an atomic mass of 50.08 grams per mole and a melting point of 840 degrees Celsius. Physically, calcium is a solid at room temperature, is slightly softer than aluminum and is silver-white color.
Calcium's chemical properties are attributed to its location in group 2 of the periodic table. As an alkaline earth metal, it is a good reducing agent for preparing other metals, such as uranium and thorium. It reacts violently when placed in water, forming calcium hydroxide, more commonly known as lime. This is the reason why water that is high in calcium causes lime buildup on the interior of pipes. Calcium also reacts rapidly when exposed to air. It develops an oxide coating, which prevents the mass of calcium from corroding. If exposed to air at a high temperature, calcium burns to produce nitride. The most common calcium isotope is Calcium-40. It has an ionic radius of 0.099 nm, a standard potential of -2.87 volts and an ionization energy of 589.6 kJ per mole. Calcium compounds are important in a number of industries. Calcium oxide, for example, is used in high intensity lights. Calcium hydroxide is useful for breaking down wood and rocks.