What Is Potassium?
QUICK ANSWER
Potassium is a chemical element with atomic number 19 and the symbol K. It's a soft, silvery-white alkali metal that reacts violently with water. Potassium is essential to all living cells, where it helps regulate fluid balance, nerve signals, and muscle contractions, and is one of the major dietary minerals humans need.
Potassium is the dietary mineral most people associate with bananas, but it's also one of the most chemically reactive metals known. Pure potassium reacts with water more violently than sodium, sometimes igniting the hydrogen produced. In the body, potassium plays a quieter but essential role keeping nerves firing, muscles contracting, and the heart beating regularly. The contrast between pure potassium and dietary potassium is one of chemistry's stranger juxtapositions.
Where is potassium on the periodic table?
Potassium has atomic number 19, the symbol K (from the Latin kalium), and sits in group 1 of the periodic table among the alkali metals, just below sodium. Its atomic mass is about 39.1. Three isotopes occur naturally: K-39 (93.3%), K-41 (6.7%), and K-40, which is radioactive with a half-life of 1.25 billion years. The K-40 in living tissue (including your body) provides a small constant source of natural radiation. Potassium was first isolated by Humphry Davy in 1807 through electrolysis of molten potassium hydroxide.
What are the properties of potassium?
Pure potassium is a soft, silvery-white metal that can be cut with a knife and quickly tarnishes in air. It has a low melting point of just 63.5°C, low enough to melt in a hot bath. Density is very low at 0.86 g/cm³, lighter than water, which is why it floats while reacting. Potassium reacts even more violently with water than sodium, often igniting the hydrogen released and producing a lavender-pink flame from potassium ions. The pure metal must be stored under oil or in inert gas to prevent reactions with moisture in the air.
Why do we need potassium in our diet?
Potassium is one of the major electrolytes in the human body, alongside sodium, calcium, and magnesium. It works opposite sodium to regulate blood pressure and fluid balance. Inside cells, potassium concentration is high; outside cells, it's low. This gradient powers nerve signals and muscle contractions. Adults need about 2,500-3,500 mg of potassium daily, and most Western diets fall short. Good sources include bananas, potatoes, sweet potatoes, beans, leafy greens, oranges, and yogurt. Low potassium can cause weakness, cramping, and heart rhythm problems.
What is potassium used for industrially?
Most mined potassium becomes potassium chloride, used heavily in agricultural fertilizers. About 95% of all potassium production worldwide goes into fertilizer. Potassium hydroxide is used to make soft soaps, biodiesel, and various chemicals. Potassium nitrate is a major component of gunpowder and fertilizers. Potassium carbonate (potash) is used in glass production, soap making, and ceramics. Potassium iodide is added to table salt as iodized salt. Pure potassium metal has limited industrial use because of its reactivity, but it's used in some specialty applications.
Potassium is one of those elements with dramatically different personalities. In pure form, it's a violently reactive metal that explodes in water. In your diet, it's a quiet electrolyte keeping nerves and heart muscles working. Both versions matter to modern life, even if most people only encounter the dietary one.
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