Elements

The Chalky Element Calcium

The Element Calcium

Introduction to the Element Calcium

The element calcium is one of the most common elements worldwide and one of the most important. Almost all organisms rely on calcium. Calcium is also prevalent in our building materials and has been since early times.

10 Interesting & Fun Facts About Calcium

  1. The name calcium comes from the Latin word for lime, “calx”.
  2. The average human contains 1kg of calcium throughout their body.
  3. Calcium does not exist as a pure metal in the environment.
  4. The body effectively absorbs calcium only when magnesium is also present.
  5. Calcium oxide produces an intense light when burned under certain conditions. At one point, the burning light lit theatres. That is where the term “in the limelight” comes from.
  6. Calcite is a form of calcium carbonate (CaCO3) that makes up the stalagmites and stalactites in caves.
  7. The most abundant inorganic element in the human body is calcium.
  8. The amount of calcium required for proper growth in many creatures varies dramatically across life stages.
  9. Due to its numerous natural compounds, calcium has been used since at least the Ancient Romans to build structures and statues.
  10. Calcium carbonate causes the lime build up around faucets when hard water is present.

The Element Calcium in the Periodic Table

Calcium under an argon atmosphere
Calcium under argon atmosphere (Source: Wikipedia Commons)

Calcium, symbol Ca, is an alkaline earth metal in the second column of the periodic table. Its atomic number is 20. It is in the fourth row of the periodic table, beneath magnesium. It has an electron configuration of [Ar]2s2. Calcium has two valence electrons and a very low electronegativity of 1.

Biological Significance of Calcium

Calcium is an essential element in the human body. There are many diseases associated with too little or too much calcium, such as osteoporosis and hypertension.

In the body, calcium is often referred to as a ‘cellular messenger’. Between the inside and outside of a cell, there is a large gradient of calcium (1:~10,000). The large differential allows for high responsiveness to changes. Hormones in the gut, skeleton, and kidneys regulate calcium ions in the body.

Calcium is the foundation of bones and teeth. Bones and teeth contain 99% of the calcium in the body. In our bones, calcium is in the mineral form hydroxylapatite (Ca10(PO4)6(OH)2), also known as calcium apatite. The same compound makes replacement bones.

The Element Calcium in the Ocean

Calcium plays an important role in the ocean ecosystem. The calcium in the ocean can come from a variety of sources including rock weathering and soil erosion. Calcium ions are present at about 410 ppm in the ocean.

Calcium is an important element for many sea creatures–coral, clams, oysters, and sea urchins to name a few. Most of the shells in the ocean are made of calcium carbonate. The sea creature extracts calcium and bicarbonate from the ocean water to make the shell. The bicarbonate comes from dissolved carbon dioxide in the water. However, as the atmospheric carbon dioxide concentration is increasing, so is the concentration in the ocean (increasing the acidity of the ocean). This disrupts the equilibrium and is causing changes in creature’s calcium carbonate shells. For example, it has already been shown that coral has a reduced ability to build its calcium carbonate skeleton.

Coral in the Great Barrier Reef
Coral outcrop on Flynn Reef (Source: Wikipedia Commons)

Calcium Applications in Today’s World

What is calcium used for?

Calcium has many different uses ranging from fertilizer to health supplements to poisons to cement. Calcium is still being innovated with today to create new technologies as well.

As a fertilizer, calcium compounds are important because plants use calcium in their cell walls. Calcium is also a messenger within the plant. Therefore, calcium fertilizers assure proper minerals are supplied.

Calcium is a critical nutrient in the body. So many supplements and medicines include calcium in them. In addition, calcium compounds make the material used for teeth fillings and bone replicates.

Possible scrubbing systems at power plants utilize calcium in the form of limestone as the main tool. The idea is to use limestone to react with the release of carbon dioxide and remove it from the air. The product is calcium bicarbonate.

For some more specific uses, see the different calcium compounds listed below.

When and How was Calcium Discovered?

The History of Calcium

Calcium compounds have been important in history for a long time. Limestone, which is primarily calcium carbonate, has been used to build statues and buildings since ~7000 BC. The ancient pyramids are also built out of a calcium compound, gypsum. Gypsum is a calcium sulfate compound.

Discovery of the Element Calcium

Elemental calcium metal was first isolated in 1808. Humphry Davy (1778 – 1829) isolated calcium after discovering several other elements which included potassium and sodium.  He isolated calcium through electrolysis, a technique he has also used to isolate other elements. Electrolysis of lime (CaO) and mercuric oxide (HgO) was performed to obtain calcium. After the electrolysis, he used distillation to purify the calcium.

Calcium Chemistry – compounds, reactions, oxidation states

Chemical Properties of Calcium

Calcium reacts readily with several molecules in the atmosphere. In nature, pure calcium does not exist because it reacts so quickly with other molecules. Calcium can react with oxygen, nitrogen, water, or several other components of air.

How Does Calcium React with Water?

Calcium reacts slowly with water. The reaction produces hydrogen gas (H2) and calcium hydroxide (Ca(OH)2). Hydrogen comes off as a gas and the calcium hydroxide precipitates. This is different than the two compounds above calcium on the periodic table, beryllium and magnesium, which do not noticeably react with water. The two compounds below calcium, strontium and barium, react similarly with water as calcium does.

Calcium Compounds

 Calcium forms many compounds. Listed below are a few of these compounds.

Calcium Hydroxide

  • Calcium hydroxide has the chemical formula Ca(OH)2 and is a white powder. Its more common name is lime. Calcium hydroxide has many uses in food processing, such as pickling. It also has uses in paper production, sewage treatment, disinfectant on farms, and cement production.

Calcium Carbonate

Stalagmites and stalactites in a German cave
Stalagmites and stalactites in a German cave (Source: Wikipedia Commons)

Calcium Chloride

  • Calcium chloride is a white powder with the chemical formula CaCl2. It prevents ice on roads and sidewalks when used as salt. Food chemistry also utilizes calcium chloride as a firming or preservative agent.

Calcium Citrate

  • Calcium citrate is a calcium salt of citric acid. Oftentimes, calcium prescriptions contain calcium citrate as the calcium source. The compound also occurs in some foods.

Calcium Gluconate

  • Calcium gluconate treats low calcium levels in the body with a prescription or as an emergency procedure. For example, when using hydrofluoric acid (HF) a tube of calcium gluconate is always kept on hand as the first form of emergency response (in addition to other safety measures). HF is very toxic and sequesters calcium from the body and can kill you with just a few milliliters very quickly. The calcium gluconate provides a source of calcium for the HF to bind with instead of the calcium from your bones

Calcium Arsenate

  • Calcium arsenate (Ca(AsO4)2) is a poisonous calcium compound. Insecticides commonly contain the molecule due to the toxicity.

Calcium Cyclamate

  • Calcium cyclamate has the chemical formula Ca(C6H11NHSO4)2. This compound is used as a sweetening agent partly because it is very soluble in water and stable at high temperatures. It provides no nutritional value. The gut does not absorb calcium cyclamate. However, bacteria in the gut can break it down to other compounds. These other compounds are sometimes cancerous. Therefore, the United States banned the compound in foods.

Calcium Hypochlorite

  • Calcium hypochlorite (Ca(OCl)2) disinfects many items. It is often present in swimming pool disinfectants, deodorants, fungicides, and bleaching agents.

Caclium Sulfate

  • Blackboard chalk is also a calcium compound! Calcium sulfate, also known as gypsum, has the chemical formula CaSO42H2O. Gypsum also fertilizes plants and makes cement.

Calcium Oxidation States

The oxidation state of calcium is +2.

Isolation of Calcium

Electrolysis is the most common technique to isolate calcium. The first isolation of calcium also utilized electrolysis. Due to its reactive nature, calcium is a difficult substance to isolate.

Physical Properties:

Calcium appears as a silvery-white metal but tarnishes quickly when exposed to air from reacting with water, oxygen, and nitrogen in the air.

Some physical properties of calcium:

  • Calcium Symbol: Ca
  • Melting point: 842°C (1548°F)
  • Boiling point: 1484°C (2703°F)
  • Density: 1.54 g/cm3
  • Atomic weight: 40.078
  • Atomic number: 20
  • Electronegativity: 1.0
  • Classification: Alkaline earth metal, Group II metal
  • Natural abundance of 4.1% in the earth’s crust, which is the 5th most abundant element in the crust.
  • Natural abundance of 8% in the moons crust
  • Electron shell configuration: [Ar]2s2
  • Isotopes: Calcium has 6 isotopes- 40Ca (96.941%), 44Ca (2.086%), 42Ca (0.647%), 48Ca (0.187%), 43Ca (0.135%), 46Ca (0.004%)
  • Found naturally in limestone, calcium carbonate, fluorite, and gypsum.
  • Toxicity: Calcium is generally non-toxic, but as with anything, too much of it can cause problems. Hypercalcemia occurs when the body contains too much calcium. Other medical issues usually cause the disbalance in calcium.

Where Can I Buy Calcium?

Pure calcium is usually sold as calcium turnings. These are available from many chemical suppliers. Be careful when handling the turnings. Follow all safety instructions supplied with the product. Pure calcium reacts with water in the air. Therefore, a dried airtight container stores elemental calcium.

Many supplements are not pure calcium but are high in calcium content if you do not need elemental calcium.

Experiments with the Element Calcium

Calcium experiments demonstrate how the ocean’s warming affects different aquatic creatures with shells made of calcium carbonate.

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