Calcium 

Calcium is a metallic element with atomic number 20 in the modern periodic table, positioned in Group 2 and Period 4. It is a member of the alkaline earth metals widely found in living organisms. Calcium can be extracted from ores such as anhydrite, gypsum, dolomite, and calcite. It is an essential component of many chemical reactions and plays a vital role in teeth and bones. 

1.0Introduction 

Sir Humphry Davy discovered calcium in 1808. It is recognised as the most abundant metal and the fifth most abundant element in the human body. Calcium ions are vital as electrolytes in cells' and organisms' physiological and biochemical processes.

Calcium is a silver-grey metal that is vital to all living things. It is extensively distributed throughout the Earth's crust, primarily as calcium fluoride, quicklime (CaO), and limestone (CaCO₃).

2.0Physical Properties of Calcium

The physical characteristics of calcium are outlined below:

3.0Chemical Properties of Calcium

The chemical characteristics of calcium determine how it behaves in chemical reactions. Understanding these characteristics is essential to comprehending the interactions and transformations that calcium goes through. The noteworthy chemical characteristics of calcium are as follows:

• Oxidation: Calcium is a deoxidizer in the steel-making process. It strengthens and improves the quality of the final product by helping to remove oxygen from the molten metal.
• Isotopes: There are six stable isotopes of calcium, namely ⁴⁰Ca, 42,⁴²Ca, ⁴³Ca, ⁴⁴Ca, ⁴⁶Ca and ⁴⁸Ca. The most abundant isotope is ⁴⁰Ca, constituting about 96.94% of naturally occurring calcium.
• Flammability: When calcium is burned with oxygen in the air, calcium oxide (CaO) is produced, which produces a bright white flame. This feature makes handling and storing it with extreme caution necessary. 
• Reactivity with Water: Calcium reacts rapidly with cold water to form calcium hydroxide (Ca(OH)₂) and hydrogen gas (H₂).

However, the reaction slows down after the initial burst due to the formation of a protective layer of calcium hydroxide on the metal's surface, which limits further reaction:Ca+2H₂O→Ca(OH)₂+H₂(g

• Reactivity with Acids: Calcium is highly reactive with acids, such as hydrochloric acid (HCl) and sulfuric acid (H₂SO₄). This reaction produces calcium salts and hydrogen gas. For example: Ca + 2HCl → CaCl₂ + H₂(g)

4.0Compounds of Calcium

Calcium forms various compounds, including calcium oxide, calcium hydroxide, calcium sulfate, calcium carbonate, and cement.

1. Calcium Oxide (CaO)

• Properties: A white, caustic solid (quicklime) with a melting point of 2,572°C reacts vigorously with water to form calcium hydroxide.
• Uses: Key in cement production, drying agents, steel-making (impurity removal), and glass/ceramics manufacturing.

2. Calcium Hydroxide (Ca(OH)₂)

• Properties: It is a colourless crystal or white powder. It is soluble in water and forms a strong alkaline solution (limewater).
• Uses: It is used in water treatment to neutralise acidity and in the food industry as an ingredient in mortars and plasters to improve soil quality.

3. Calcium Sulfate (CaSO₄)

• Properties: It is a white solid, occurring as gypsum (dihydrate) and anhydrite (anhydrous).
• Uses: In the construction industry for, drywall and plaster. And as a coagulant in tofu production.

4. Calcium Carbonate (CaCO₃)

• Properties: It is a white, odourless powder or crystal; it is insoluble in water but reacts with acids.
• Uses: As a dietary calcium supplement and antacid, it produces lime and cement.

5.0Uses Of Calcium

The earliest recorded use of calcium dates back to the Romans, who used it to make calcium oxide (quicklime). By 975 C.E., calcium sulfate (Plaster of Paris) was documented for medical use.

Calcium is available in various forms, including limestone, chalk, marble (calcium carbonate), and minerals like calcite and pearls.

• Calcium carbonate is used as an antacid and calcium supplement.
• Calcium nitrate is widely used as a fertiliser.
• Calcium is essential for maintaining healthy bones and teeth.
• It assists in muscle movement by transmitting messages from the brain to different body parts.
• Calcium ions act as carriers between cells in multicellular organisms.
• It aids in the release of hormones and enzymes in the body.
• Calcium is extensively used in steelmaking, forming compounds with oxygen and sulfur.
• Several calcium compounds are used as food additives and in the pharmaceutical industry.