1. General Information
- Symbol: K
- Atomic Number: 19
- Atomic Mass: 39.10 u
- Group: 1 (Alkali Metals)
- Period: 4
- Block: s-block
- Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
- Valence Electrons: 1
- Phase at Room Temperature: Solid
2. Isotopes of Potassium
| Isotope | Protons | Neutrons | Abundance | Notes |
|---|---|---|---|---|
| ³⁹K | 19 | 20 | 93.3% | Most abundant and stable. |
| ⁴⁰K | 19 | 21 | 0.0117% | Radioactive, used in dating rocks. |
| ⁴¹K | 19 | 22 | 6.7% | Stable. |
3. Physical Properties
- Color: Silvery-white
- Odor: Odorless
- Density: 0.89 g/cm³
- Melting Point: 63.5°C
- Boiling Point: 759°C
- State at STP: Solid
- Soft Metal: Can be cut with a knife.
4. Chemical Properties
- Highly Reactive (Especially with Water):
- Reacts violently, producing potassium hydroxide (KOH) and hydrogen gas (H₂).
- Oxidizes Rapidly in Air:
- Forms potassium oxide (K₂O) or potassium peroxide (K₂O₂).
- Stored in Oil:
- Prevents reaction with moisture and air.
- Flammable:
- Burns with a lilac (purple) flame.
Reaction with Water:
2K + 2H₂O → 2KOH + H₂↑
Reaction with Oxygen:
4K + O₂ → 2K₂O
5. Occurrence and Abundance
- 7th most abundant element in Earth’s crust.
- Found in:
- Minerals: Sylvite (KCl), Carnallite (KMgCl₃·6H₂O), Potash.
- Seawater: As potassium ions (K⁺).
- Essential for Biological Systems – Present in all living cells.
6. Industrial Production of Potassium
- Electrolysis of Potassium Chloride (KCl):
2KCl → 2K + Cl₂ (Electrolysis)
- Thermal Reduction:
KCl + Na → K + NaCl (at high temperatures)
7. Uses of Potassium
| Application | Description |
|---|---|
| Fertilizers | Potassium chloride (KCl) and potassium sulfate (K₂SO₄). |
| Glass and Ceramics | Improves durability and melting point. |
| Soap and Detergents | Potassium hydroxide (KOH) in liquid soaps. |
| Medicine and Supplements | Essential for nerve and muscle function. |
| Gunpowder and Fireworks | Potassium nitrate (KNO₃) as an oxidizer. |
| Electronics | Used in specialized batteries. |
8. Important Potassium Compounds
| Compound | Formula | Use |
|---|---|---|
| Potassium Chloride | KCl | Fertilizer, salt substitute. |
| Potassium Hydroxide | KOH | Soaps, cleaning products. |
| Potassium Nitrate | KNO₃ | Fertilizers, fireworks, gunpowder. |
| Potassium Carbonate | K₂CO₃ | Glass, soap, and detergents. |
| Potassium Permanganate | KMnO₄ | Disinfectant, water treatment. |
| Potassium Sulfate | K₂SO₄ | Fertilizer. |
9. Biological Importance of Potassium
- Essential for Life:
- Regulates nerve impulses, muscle contractions, and fluid balance.
- Maintains cell membrane potential through the sodium-potassium pump.
- Daily Requirement:
- Adults: 3,500–4,700 mg/day.
- Deficiency Symptoms (Hypokalemia):
- Fatigue, muscle weakness, irregular heartbeat.
10. Potassium in Environmental Chemistry
- Nutrient Cycle:
- Potassium is essential for plant growth and is part of the soil nutrient cycle.
- Erosion and Weathering:
- Releases potassium into soil from rocks.
- Fertilizer Runoff:
- Excess potassium can disrupt aquatic ecosystems.
11. Safety and Hazards
- Highly Flammable:
- Potassium ignites easily and reacts violently with water.
- Corrosive (KOH):
- Can cause burns upon contact.
- Asphyxiation Risk:
- Hydrogen gas produced during reactions can ignite or displace oxygen.
Handling Precautions:
- Store in mineral oil or inert atmosphere.
- Use protective gloves and goggles.
- Keep away from water and open flames.
Fun Facts About Potassium:
- The name “potassium” comes from potash, an early source of potassium salts.
- Discovered in 1807 by Sir Humphry Davy through electrolysis.
- Potassium is responsible for the purple color in fireworks.
- Bananas are famous for their potassium content, but potatoes and avocados contain more!