The elemental calcium
What comes to your mind when you hear the word calcium? Supplements that strengthen your bones, perhaps? But there are much more to it than that! For example, did you know that calcium in its elemental form is a metal (pictured above)? That calcium is a major ingredient in construction work? Here is an overview of calcium in its elemental form, as well as importance of its compounds in our daily lives.
The name calcium originates from a Latin word for lime, calx. Limestone, the starting material of lime, is a form of calcium compound, calcium carbonate (CaCO3). Romans used limestone as early as in the first century, and the material has been a major building component throughout human history, such as plaster and concrete. Examples of famous structures built using limestone include the Great Pyramid of Giza, the Colosseum of Rome, and the Empire State Building of New York.
Despite its common use, the elemental calcium in its pure form (pictured above) cannot be found in nature since it readily reacts with air and water. It wasn’t until 1808, when Humphry Davy, a Cornish chemist, carried out an electrolysis reaction of a mixture of lime and mercury oxide, that the elemental calcium was isolated and a new element was discovered.
Although calcium cannot be found by itself in nature, calcium compounds are abundant. All together, this makes calcium the 5th most common element in Earth’s crust (by weight), consisting greater than 3%. (A tidbit: Martian soil also contains 3-8% calcium). Some of calcium compounds abundant in nature are limestone (CaCO3) and gypsum (calcium sulfate, or CaSO4). The world-famous White Cliffs of Dover in the English coastline (pictured above) are made of limestone. Gypsum crystals, such as the ones found in a cave in Chihuahua, Mexico, are some of the largest crystals in the world (pictured below) – people can even walk on them! Calcium carbonate also forms stone “icicles” and pillars, called stalactites and stalagmites, in caves.
Calcium is also an essential element in organisms. An average person contains about 1kg of calcium. Calcium phosphate (CaPO4) is the major building component of bones and teeth; 99% of calcium in the body is found in bones and teeth. The rest of calcium in the body is equally necessary in performing important bodily functions, such as muscle contraction, nerve transmission, and hormone secretion. Calcium deficiency may have a long-term impact on health, resulting in weaker bones. We get calcium into our bodies through food sources, such as dairy products (milk, cheese, yogurt, etc.), almonds, vegetables (kale, spinach, tomatoes, etc.), and tofu. Because bones rapidly grow in children and teens, recommended daily calcium intake in ages 9-18 is higher than adults, at 1300mg of calcium, equivalent to about 4 glasses of milk. Vertebrates, like us humans, are not the only ones dependent on calcium; calcium carbonate is the main component of shells and mollusks.
Calcium also has diverse use outside of living things, namely in constructions and chemical industry. Limestone (calcium carbonate) has been used as mortar and plaster for buildings throughout history. Slaked lime (calcium hydroxide) is a major component of cement and is also used as a soil conditioner and water treatment to reduce acidity. Calcium is also an important element in the chemical industry; it is used in preparing other metals (thorium, uranium, etc.) or in the preparation of aluminum, copper, and lead alloys.
Finally, here are some more snippets of facts on calcium:
– Burning lime (calcium oxide, or CaO) in an oxyhydrogen flame produces intense light. This lighting system, known as limelight, was commonly used in the 19th century for theatric stage lighting, until they were eventually replaced by electricity. Today, in the limelight still describes someone in the focus of public attention, much like an actor under the spotlight.
– Calcium salts are used in fireworks to produce deep orange color. Check out what colors other salts burn in this post about flame test.
– Calcium is essential and the 7th most abundant element in the human body. 99% of calcium in the body is found in bones and teeth. Find out how much calcium is in your body based on your weight using this calculator.
This article was written for CurioCity, part of Let’s Talk Science. Many thanks to the peer writers and editors at CurioCity for their great suggestions. Read the final draft edited by the CurioCity editor here.