1. General Information
- Symbol: Ca
- Atomic Number: 20
- Atomic Mass: 40.08 u
- Group: 2 (Alkaline Earth Metals)
- Period: 4
- Block: s-block
- Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
- Valence Electrons: 2
- Phase at Room Temperature: Solid
2. Isotopes of Calcium
| Isotope |
Protons |
Neutrons |
Abundance |
Notes |
| ⁴⁰Ca |
20 |
20 |
96.9% |
Most abundant, stable. |
| ⁴²Ca |
20 |
22 |
0.65% |
Stable. |
| ⁴³Ca |
20 |
23 |
0.14% |
Stable. |
| ⁴⁴Ca |
20 |
24 |
2.08% |
Stable. |
| ⁴⁸Ca |
20 |
28 |
0.19% |
Rare, used in nuclear research. |
3. Physical Properties
- Color: Silvery-white
- Odor: Odorless
- Density: 1.55 g/cm³
- Melting Point: 842°C
- Boiling Point: 1,484°C
- State at STP: Solid
- Soft Metal: Can be cut with a knife.
4. Chemical Properties
- Moderately Reactive:
- Reacts readily with water to form calcium hydroxide (Ca(OH)₂) and hydrogen gas (H₂).
- Reacts with oxygen to form a thin layer of calcium oxide (CaO).
- Forms Alkaline Solutions in water.
- Burns with a Bright Orange-Red Flame.
Reaction with Water:
Ca + 2H₂O → Ca(OH)₂ + H₂↑
Reaction with Oxygen:
2Ca + O₂ → 2CaO
5. Occurrence and Abundance
- 5th most abundant element in Earth’s crust.
- Found in:
- Minerals: Limestone (CaCO₃), Gypsum (CaSO₄·2H₂O), Fluorite (CaF₂).
- Bones and Teeth: Makes up 99% of body calcium in humans.
- Seawater: Contains calcium ions (Ca²⁺).
6. Industrial Production of Calcium
- Electrolysis of Molten Calcium Chloride (CaCl₂):
CaCl₂ → Ca + Cl₂
- Thermal Reduction:
CaO + Al → Ca + Al₂O₃
7. Uses of Calcium
| Application |
Description |
| Construction |
Limestone and gypsum used in cement and plaster. |
| Steel Production |
Removes impurities as a flux. |
| Chemical Manufacturing |
Produces calcium compounds (e.g., CaCl₂, Ca(OH)₂). |
| Pharmaceuticals |
Supplements and antacids. |
| Glass and Ceramics |
Calcium carbonate (CaCO₃) strengthens glass. |
| Fertilizers |
Calcium nitrate (Ca(NO₃)₂) enriches soil. |
8. Important Calcium Compounds
| Compound |
Formula |
Use |
| Calcium Carbonate |
CaCO₃ |
Chalk, limestone, antacids. |
| Calcium Oxide (Quicklime) |
CaO |
Cement, steel, and paper. |
| Calcium Hydroxide |
Ca(OH)₂ |
Plaster, water treatment. |
| Calcium Chloride |
CaCl₂ |
De-icing roads, food preservative. |
| Calcium Nitrate |
Ca(NO₃)₂ |
Fertilizer. |
| Calcium Sulfate |
CaSO₄ |
Plaster of Paris, drywall. |
9. Biological Importance of Calcium
- Essential for Life:
- Builds bones and teeth (hydroxyapatite).
- Regulates nerve function, muscle contractions, and blood clotting.
- Cellular Function:
- Calcium ions (Ca²⁺) play a role in cell signaling and enzyme activation.
- Daily Requirement:
- Adults: 1,000–1,200 mg/day.
10. Calcium in Environmental Chemistry
- Water Hardness:
- Calcium ions cause hard water, forming scale in pipes.
- Carbonate Cycle:
- Calcium carbonate in oceans helps regulate CO₂ levels through the carbon cycle.
- Soil Health:
- Calcium enhances soil structure and plant growth.
11. Safety and Hazards
- Reacts with Water:
- Generates heat and hydrogen gas, which can ignite.
- Irritant:
- Calcium hydroxide (slaked lime) can cause skin and eye burns.
- Non-Toxic in Small Quantities:
- Excessive intake can cause hypercalcemia (calcium buildup in the body).
Handling Precautions:
- Store in dry environments to prevent reactions with moisture.
- Use protective gear (gloves, goggles) when handling calcium compounds.
Fun Facts About Calcium:
- Calcium was isolated in 1808 by Sir Humphry Davy.
- Calcium carbonate forms stalactites and stalagmites in caves.
- Calcium ions are essential for the “glow” in fireflies.
- Bone fossils and shells are primarily composed of calcium minerals.