Potassium
| Element | Potassium |
| Symbol | K |
| Atomic Number | 19 |
| Molar Mass | 39.1 gmol-1 |
| Electron Configuration | [Ar]4s1 |
| Normal State | solid metal |
| Density @STP | 0.86 g cm-3 |
| Melting Point | 63oC |
| Boiling Point | 759oC |
| Stable Isotopes | 39K, 40K, 41K |
| Atomic Radius | 235 pm |
| Ionic Radius | 138 (1+) pm |
| Electronegativity (Pauling) | 0.82 |
| Ionization Energy (1st) | 419 kJ mol-1 |
| Ionization Energy (2nd) | 3051 kJ mol-1 |
| Ionization Energy (3rd) | 4411 kJ mol-1 |
| Molar Heat Capacity | 29.6 J K-1mol-1 |
| Standard Molar Entropy | 64.7 J K-1mol-1 |
| Enthalpy of Fusion | 2.4 kJ mol-1 |
| Enthalpy of Vapourization | 77.53 kJ mol-1 |
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- Potassium is a silvery grey soft highly reactive alkali metal element
- Potassium discovered and first isolated by Humphry Davy (1807)
- Potassium was first isolated from potash, the ashes of plants, from which its name derives
- Potassium in nature occurs only in ionic salts
- Potassium oxidizes rapidly in air and reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction
- Potassium has three natural isotopes, 40K is radioactive and is the most common radioisotope in the human body
- Agricultural fertilizers containing potassium, accounting for most of potassium chemical production
- Potassium is the second least dense metal after lithium
- Potassium is a soft solid with a low melting point, and can be easily cut with a knife
- Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air
- In a flame test, potassium and its compounds emit a lilac colour
- Potassium hydroxide KOH is a strong base used to control pH and to manufacture potassium salts. It is also used to saponify fats and oils in industrial cleaners
- Potassium nitrate (KNO3) or saltpeter is the oxidant in gunpowder and an important agricultural fertilizer
- Potassium cyanide (KCN) is used industrially to dissolve copper and precious metals
- Potassium carbonate (K2CO3 or potash) is used in the manufacture of glass, soap, color TV tubes, fluorescent lamps, textile dyes and pigments
- Potassium permanganate (KMnO4) is an oxidizing, bleaching and purification substance and is used for production of saccharin
- Potassium chlorate (KClO3) is added to matches and explosives
- Potassium bromide (KBr) was formerly used as a sedative and in photography
- Potassium chromate (K2CrO4) is used in inks, dyes, stains (bright yellowish-red color), explosives, fireworks, tanning of leather
- Potassium superoxide, KO2 an orange solid that acts as a portable source of oxygen and a carbon dioxide absorber.
- Potassium ions are vital for the functioning of all living cells
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