What is Calcium?
Calcium is an alkaline earth metal. Group 2 elements of the modern periodic table are known as alkaline earth metals (except Beryllium). Calcium being an alkaline earth metal, it forms a dark oxide-nitrate layer due to its high reactivity and when exposed to the air. Its physical and chemical properties are most similar to its heavier homologs strontium and barium. Sir Humphry Davy discovered calcium in 1808. Calcium is found to be the most abundant metal and when talking about the human body it is the fifth most abundant element in the human body. In the physiological and biochemical processes of organisms and cells, calcium ions have an important role as electrolytes. There are various uses of calcium and it is one of the most important chemical elements.
Calcium Element
The chemical symbol of calcium is 'Ca'.Its atomic number is 20 and its atomic mass is 40.078 g/mol.
The location of calcium elements in the modern periodic table is the 2nd group,4th period, and 's' block. Its electronic configuration is ArAr4s². At 20°c, this element is present in solid-state. It has a melting point of 842°c and a boiling point of 1484°c. The density of calcium is 1.54 gm/cm³.Important isotopes of calcium include 48Ca, 46Ca, 44Ca, 43Ca, 42Ca, and 40Ca.CAS number for calcium is 7440-70-2.
Calcium Symbol
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Atomic Structure of Calcium
The nuclear composition of an atom of calcium-40 (atomic number: 20), the most common isotope of this element consists of 20 protons and 20 neutrons. 20 electrons occupy available electron shells (rings).
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A number of Energy Levels: 4
First Energy Level: 2
Second Energy Level: 8
Third Energy Level: 8
Fourth Energy Level: 2
So we can see it has 2 electrons in its valence shell, hence its valency is 2. The crystal structure of calcium is cubic. The atomic data of calcium is as follows:
Covalent radius (Å): 1.74
Electron affinity: 2.369 (kJ mol−1)
Electronegativity: 1.00 (Pauling scale)
Atomic Data of Calcium
Ionisation Energies (kJ mol−1)
Uses of Calcium
The biological use of calcium is to provide strength and structure to the skeleton. It is vital for the maintenance of bones and teeth.
Calcium ions on bone surfaces interact with those present in the bodily fluids, therefore enabling ion exchange, which is essential in maintaining the balance of calcium in the blood and bone.
Calcium circulating in the blood is involved in several vital processes including coagulation, nerve signal transmission, hormone signaling, and muscle contraction.
Calcium may be used as a reducing agent in the process of metal extraction.
Calcium is also used in the production of some metals, as an alloying agent.
Calcium carbonate is used to make cement and mortar and also in the glass industry.
Properties of Calcium
Properties of calcium can be categorized as physical and chemical.
Physical Properties of Calcium
These are those properties that can be observed using our senses such as colour, lustre, freezing point, boiling point, melting point, density, hardness, and odour. These are observed without changing the substance into another substance. They are:
- Colour: Silvery-white metallic
- Phase: Solid
- Hardness: Relatively soft metal
- Crystalline structure: Cubic
- Ductility: It can be beaten into extremely thin sheets. It can be pressed, rolled, and cut
- Malleability: Capable of being shaped or bent
- Melting point: Melting point is 842°C
- Boiling point: Boiling point is 1484°C
Chemical Properties of Calcium
These are only observable during a chemical reaction. These properties determine how calcium behaves when changing from one substance to another or when reacting with other substances. They are:
- Chemical Formula: Ca
- Oxidation: Used as a deoxidizer in steel
- Isotopes: Six
- Compounds: Compounds include limestone, marble, gypsum, etc.
- Flammability: When heated in air or in oxygen it ignites
- Reactivity with water: Reacts with cold water rapidly at first, but the reaction is then slowed due to the formation of a film of Calcium hydroxide - \[Ca(OH)_{2}\]
- Reactivity with acids: Highly reactive
Calcium Compounds
Important compounds of calcium are:
Calcium oxide or Quicklime (CaO)
Calcium hydroxide or Slaked lime \[(Ca(OH)_{2})\]
Calcium Carbonate \[(CaCO_{3})\]
Calcium Sulphate or Plaster of Paris \[(CaSO_{4} . \frac{1}{2}H_{2}O)\]
Facts About Calcium
Humans have known about calcium and its compounds before the Greeks and Romans.
Romans made use of lime in their concrete and termed it “Calx.”
Davy could separate pure calcium in 1808. He was the original chemist to do so.
It turns tougher as a silver-coloured metal once it is refined.
Calcium is used in fireworks to add orange colour.
Calcium in Living Organisms
Calcium is found in all living and dead organisms since it is necessary for life. Aquatic animals' shells, eggshells, and snail shells are all made up mostly of calcium carbonate, which dissolves in acid. Aside from skeletal activities, the Ca2+ ion is important in signal transduction pathways, muscle function, neurotransmission, fertilization, and enzymatic activity in mammals and many species. Calcium is also found in the membrane, cell wall, and vacuole of plants. Coral reefs, which are mainly calcium carbonate, are one of the most important calcium deposits. Over the course of their lives, coral secretes calcium carbonate and ultimately dies, allowing new coral to grow on top of their calcium carbonate framework. These calcium deposits build into huge reefs over a long period of time, some of which can be seen from space. Photosynthesis in sea plants is preferred in these areas due to the abundance of sunshine and minerals such as calcium, allowing fish and other marine life to thrive. Calcium phosphate makes up the majority of human bones. Cow milk is likewise high in calcium phosphate, which is why human society encourages youngsters and others who are at risk of osteoporosis to consume milk.
Osteoporosis
The National Institutes of Health estimates that half of all women over 50 and a quarter of all males over 50 will break a bone as a result of osteoporosis. Osteoporosis is most common in postmenopausal white and Asian women. In women with osteoporosis, about 25% will have a vertebral deformity, and 15% will fracture their hip. Men can also break their hips due to osteoporosis, albeit not as frequently as women. Hip fractures are linked to an increased risk of mortality in the first year following the break. Osteoporosis is caused by a combination of circumstances:
Not enough calcium in the diet.
Age over 50.
Small, thin body build.
Family history of osteoporosis.
Smoking.
Use of certain medications such as breast cancer treatments, seizure medications, steroids.
Symptoms of Osteoporosis
Bone loss symptoms do not appear until osteoporosis has progressed. Osteoporosis may not cause any symptoms at all in its early stages. As osteoporosis progresses, the following symptoms may appear:
Breaking bones easily.
Back pain.
Stooped posture.
Gradual loss of height.
FAQs on Calcium
1. What is the electronic configuration of Calcium and how does it determine its position in the periodic table?
Calcium (Ca) has an atomic number of 20. Its full electronic configuration is 1s²2s²2p⁶3s²3p⁶4s². The condensed configuration is [Ar] 4s². This structure places Calcium in the modern periodic table as follows:
- Group 2: It has two valence electrons in its outermost 's' orbital.
- Period 4: The principal energy level of its valence electrons is n=4.
- s-block: The last electron enters the s-orbital.
2. Why is Calcium classified as an alkaline earth metal?
Calcium is classified as an alkaline earth metal based on the properties of its compounds and its natural occurrence. The two main reasons are:
- The term 'alkaline' refers to the fact that its oxide (Calcium Oxide, CaO) and hydroxide (Calcium Hydroxide, Ca(OH)₂) are basic in nature when dissolved in water.
- The term 'earth' was historically used by alchemists to describe non-metallic substances that were insoluble in water and stable on heating, a characteristic of their oxides. These metals are also found abundantly in the Earth's crust.
3. What are some important industrial compounds of Calcium and their uses?
Several compounds of Calcium are crucial for various industries. The most significant ones include:
- Calcium Carbonate (CaCO₃): Found as limestone and marble, it is the primary raw material for making cement, mortar, and lime.
- Calcium Oxide (CaO) or Quicklime: Used as a flux in metallurgy, in sugar refining, and for making bleaching powder.
- Calcium Hydroxide (Ca(OH)₂) or Slaked Lime: Used in the leather industry, for water softening, and in mortar and plaster.
- Calcium Sulphate (CaSO₄·½H₂O) or Plaster of Paris: Widely used in construction for finishing walls and ceilings, and for making surgical casts to set fractured bones.
4. How does Calcium's reactivity with water differ from other Group 2 metals?
Calcium's reactivity with water is moderate compared to other elements in its group. It reacts with cold water to produce calcium hydroxide and hydrogen gas. However, the reaction slows down as a layer of sparingly soluble calcium hydroxide [Ca(OH)₂] forms on the metal's surface, preventing further contact with water. In contrast, metals above it like Beryllium show almost no reaction, while metals below it, such as Strontium and Barium, react much more vigorously and completely with water.
5. What is the difference between the structural and signalling roles of Calcium in the human body?
In the human body, calcium primarily exists as the ion Ca²⁺ and serves two distinct functions:
- Structural Role: About 99% of the body's calcium is stored in bones and teeth in the form of hydroxyapatite [Ca₅(PO₄)₃(OH)]. This provides the hard, rigid framework essential for physical support and protection.
- Signalling Role: The remaining 1% of calcium circulates in the blood and soft tissues as Ca²⁺ ions. This small amount is vital for cell signalling pathways that control critical processes like muscle contraction, nerve impulse transmission, hormone secretion, and blood coagulation.
6. Why does Calcium impart a characteristic brick-red colour to a flame?
When a calcium salt is introduced into a flame, the heat provides energy to its valence electrons, causing them to jump to a higher, unstable energy level. As they immediately fall back to their original, stable energy level, they release the absorbed energy in the form of light. For Calcium, the specific wavelength of the emitted light falls in the visible spectrum corresponding to a characteristic brick-red colour. This principle is used in analytical chemistry for the qualitative detection of calcium and in pyrotechnics to create orange and red fireworks.
7. What is the chemical principle behind using Calcium Carbonate (limestone) in steel manufacturing?
In steel manufacturing, limestone (CaCO₃) is used as a flux in the blast furnace. Its purpose is to remove acidic impurities, primarily silicon dioxide (SiO₂), which is present as sand in the iron ore. The high temperature in the furnace decomposes the calcium carbonate into calcium oxide (quicklime) and carbon dioxide: CaCO₃(s) → CaO(s) + CO₂(g). The basic calcium oxide (CaO) then reacts with the acidic impurity silicon dioxide (SiO₂) to form a molten slag, calcium silicate (CaSiO₃): CaO(s) + SiO₂(s) → CaSiO₃(l). This slag is less dense than the molten iron and floats on top, allowing it to be easily separated.
