Calcium
Simplified 2D Bohr model:Central red circle is the nucleus (proton). Blue ring represents the electron's orbit. Small blue dot is the electron. Note: This basic model doesn't show quantum behavior.
CLASSIFICATION:
Alkaline Earth Metal
Belonging to Group 2 of the periodic table, calcium readily loses two electrons to achieve a stable electron configuration, forming a +2 cation. Its reactivity, especially with air and water, dictates its natural occurrence in compound forms.
40.078 u
Appearance: Silvery white metallic luster
Calcium, a cornerstone of life and industry, is a reactive alkaline earth metal renowned for its silvery-white luster. As the fifth most abundant element in the Earth's crust, calcium plays a pivotal role in shaping our world, from the formation of mountains to the strength of our bones. Its versatility extends to a myriad of applications, including construction, metallurgy, and even the regulation of our heartbeats.
20
20
20 (most abundant isotope)
eV
4. Discovery and History
842 °C
1484 °C
1.55 g/cm³ at 20 °C
197 pm
26.2 cm³/mol
176 pm
25.929 J/(mol·K)
201 W/(m·K)
3810 m/s at 20 °C
1.55 g/cm³ at 20 °C
1.75
201 W/(m·K)
170 MPa
0.647 J/(g·K) at 25 °C
22.3 µm/(m·K) at 25 °C
Transitions from solid to liquid at 842 °C and boils at 1484 °C under standard atmospheric pressure.
Calcium reacts vigorously with water, generating calcium hydroxide and hydrogen gas. It readily combines with oxygen to form calcium oxide and reacts with acids to produce hydrogen gas and corresponding calcium salts.
+2
-2.87 V for the Ca²⁺/Ca couple
Calcium predominantly exhibits a +2 oxidation state, reflecting the loss of its two valence electrons. Its ionic nature and strong reducing properties govern its chemical behavior in various reactions.
Paramagnetic
3.91 × 10⁻⁸ Ω·m at 20 °C
-4.1 x 10⁻¹¹ m³/C
Not applicable for metals
High reflectivity due to its metallic nature, especially when freshly cut.
Calcium exhibits characteristic spectral lines, such as the prominent violet line at 422.7 nm, which are used in astronomical spectroscopy to identify its presence in stars and interstellar clouds.
n = 4 for calcium's valence electrons (l = 0 for the s orbital)
Total Electrons: 20, Shells: 1s², 2s² 2p⁶, 3s² 3p⁶, 4s²
-6.1132 eV for the ionization energy, representing the energy required to remove an electron from the outermost 4s orbital.
[Ar] 4s²
The electron configuration reveals two valence electrons in the outermost 4s orbital, readily available for bonding and contributing to calcium's reactivity and +2 oxidation state.
Terrestrial Abundance
Calcium is widely distributed in the Earth's crust, primarily found in minerals like calcite (CaCO3), dolomite (CaMg(CO3)2), and gypsum (CaSO4·2H2O). These minerals form sedimentary rocks like limestone and marble, shaping landscapes and providing essential resources.
Face-centered cubic (FCC)
Temperature: Below 450 °C
At room temperature, calcium adopts a face-centered cubic structure, where each calcium atom is surrounded by twelve equidistant neighbors.
+2
The dominant oxidation state of calcium, reflecting its tendency to lose two electrons and form stable ionic compounds.
Calcium Carbonate (CaCO3)
CaCO3
Found in limestone, marble, and shells, calcium carbonate is a ubiquitous compound with diverse applications. It serves as a building material, an antacid, and a key ingredient in paper, plastics, and paints.
Calcium Hydroxide (Ca(OH)2)
Ca(OH)2
Commonly known as slaked lime, calcium hydroxide is produced by hydrating calcium oxide. Its applications span water treatment, mortar and plaster production, and pH adjustment in various industrial processes.
Calcium Sulfate (CaSO4)
CaSO4
Calcium sulfate exists in various forms, including gypsum (hydrated form) and anhydrite (anhydrous form). Gypsum is widely used in plaster, drywall, and cement, while anhydrite finds applications in construction and as a drying agent.
Calcium Chloride (CaCl2)
CaCl2
A versatile compound, calcium chloride is employed as a deicing agent, a desiccant, and in food processing. Its hygroscopic nature makes it effective in absorbing moisture from the environment.
Calcium Phosphate (Ca3(PO4)2)
Ca3(PO4)2
A major component of bones and teeth, calcium phosphate is essential for biological mineralization. It is also used as a fertilizer and in the production of phosphorus-containing compounds.
422.7 nm nm
Strong
Visible (violet)
610.3 nm nm
Medium
Visible (orange)
612.2 nm nm
Medium
Visible (orange)
616.2 nm nm
Medium
Visible (red)
17. Practical Applications
Construction Materials
Calcium compounds, particularly calcium carbonate and calcium sulfate, are fundamental components of cement, concrete, mortar, and plaster, shaping the infrastructure of our modern world.
Metallurgical Processes
Calcium's reducing power makes it an effective agent in extracting metals like uranium, zirconium, and thorium from their ores. It also serves as a deoxidizer and alloying element in steel production.
Biological Significance
Calcium ions (Ca²⁺) are indispensable for life, regulating muscle contraction, nerve transmission, blood clotting, and enzyme activity. They also form the structural basis of bones and teeth, ensuring skeletal integrity.
Food and Nutrition
Calcium is an essential nutrient for human health, crucial for bone health, muscle function, and nerve transmission. It is found in dairy products, leafy green vegetables, and fortified foods.
Environmental Remediation
Calcium compounds, such as lime (calcium oxide), are used to treat acidic soils and wastewater, neutralizing acidity and improving soil quality and water purity.
26. Synthesis and Production
Calcium metal is primarily produced through the electrolysis of molten calcium chloride (CaCl2). This process involves passing an electric current through the molten salt, causing calcium ions to be reduced at the cathode, forming calcium metal.
Most industrial calcium is extracted from limestone (CaCO3) through a process called calcination. Limestone is heated to high temperatures, driving off carbon dioxide (CO2) and leaving behind calcium oxide (CaO), also known as quicklime. Quicklime can be further processed to obtain calcium metal or used directly in various applications.
Global calcium production is estimated to be several million tons per year, with China being the largest producer, followed by the United States and Russia.
20. Economic Data
Market Price: Variable, depending on form and purity
Producing Countries: China, the United States, and Russia are among the leading producers of calcium and calcium-containing minerals, with significant contributions from India, Brazil, and several European countries.
Industrial Use: N/A
Description: N/A
18. Biological Role
Essential Element
Calcium ions (Ca²⁺) are indispensable for life, participating in a multitude of physiological processes. They play a critical role in: * **Bone and teeth formation:** As the primary mineral component of bones and teeth, calcium provides structural integrity and strength. * **Muscle contraction:** Calcium ions trigger muscle contraction by facilitating the interaction of muscle proteins. * **Nerve transmission:** Calcium ions are involved in the release of neurotransmitters, enabling communication between nerve cells. * **Blood clotting:** Calcium ions are essential for the cascade of reactions leading to blood clot formation. * **Enzyme activity:** Calcium acts as a cofactor for various enzymes, modulating their activity and influencing metabolic processes.
Calcium usage in foods and supplements is subject to regulations to ensure safety and quality. Industrial calcium production is regulated to minimize environmental impacts, including air and water pollution, and to ensure worker safety.
There are few legal restrictions on calcium itself. However, regulations may apply to specific calcium compounds depending on their potential hazards and applications.
19. Health and Environmental Impact
Calcium is essential for human health, but both deficiency and excess intake can have adverse effects. Calcium deficiency can lead to osteoporosis and increased risk of fractures, while excessive calcium intake can contribute to kidney stones and interfere with the absorption of other minerals.
The mining and processing of calcium-containing minerals can have environmental impacts, including habitat disruption, soil erosion, and greenhouse gas emissions. Sustainable mining practices and the use of recycled calcium materials are crucial for mitigating these impacts.
27. Environmental Safety
Calcium metal itself poses minimal health risks, but calcium compounds can vary in toxicity. Excessive calcium intake can lead to hypercalcemia, while calcium dust may irritate the eyes, skin, and respiratory tract.
Handling calcium metal necessitates standard safety gear, including gloves and eye protection. Calcium compounds should be handled according to their specific safety data sheets, with attention to potential hazards and exposure limits.
Handling: N/A
Storage: N/A
First Aid Measures: N/A
23. Future Predictions
Advancements in Bioavailability
Research efforts are focused on improving the bioavailability of calcium from dietary sources and supplements, potentially through the development of novel formulations and delivery systems that enhance absorption and utilization.
Biomaterials and Tissue Engineering
Calcium-based biomaterials are being explored for applications in tissue engineering and regenerative medicine, with the potential to create scaffolds for bone regeneration and other medical applications.