What is Potassium? | Definition, Properties, Compounds, & Facts

What is Potassium?

Potassium is the fourth element in the first column of the periodic table. It is classified as an alkali metal. The potassium atom has 19 electrons and 19 protons with one valence electron in the outermost shell. Potassium is considered chemically similar to sodium, the top alkali metal on the periodic table.

Highlights of Potassium:

Symbol K
Atomic Number 19
Atomic Weight 39.0983
Classification Alkaline metal
Phase at Room Temperature Solid
Density 0.86 grams per cm cubed
Melting Point 63.38°C, 146.08°F
Boiling Point 759°C, 1398°F
Discovered by Sir Humphry Davy in 1807

Characteristics and Properties

Under normal conditions, potassium is a soft, silvery-white metal. It is so soft that it can be easily cut with a knife. When cut, the exposed metal quickly tarnishes and forms a translucent oxide layer.

Potassium has a very low melting point, so even a candle can melt it. When burned, it produces a light purple flame. Potassium also has a very low density and is the second lowest density metal after lithium. It is so light that it can float in water.

Chemically, potassium is a very active metal. It reacts violently with water, producing heat and hydrogen gas. It also reacts with many other elements and substances such as oxygen, acids, sulfur, fluorine and nitrogen.

Where is Potassium found on Earth?

Because potassium reacts very readily with water, it is not found as an element in nature. Instead, it is found in various minerals such as sylvit, carnallite, langbeinite and kainite. Most minerals that contain potassium are called potassium.

Consisting of about 2.1% by weight of the earth’s crust, potassium is the eighth most abundant element in the earth’s crust. It can also be found in seawater, where it is also the eighth most abundant element.

How is Potassium used today?

The most common use of potassium is potassium chloride (KCl) which is used to make fertilizers. Potassium is very important for plant growth.

Industrial uses of potassium include soaps, detergents, gold mining, dyes, glass manufacturing, gunpowder, and batteries.

Potassium also plays an important role in our body. It is used in muscle contraction, fluid and pH balance, bone health, and helps prevent kidney stones. It is the eighth most abundant element in the human body by weight.

How was it discovered?

Potassium was first isolated by British chemist Sir Humphry Davy in 1807. He used electricity to separate the element potassium from salt.

Where did potassium get its name?

Potassium gets its name from the potassium salt from which potassium was first isolated. The element’s symbol K is derived from the Latin word “kalium, which means potash.


There are three naturally occurring potassium isotopes: K-39, 40, and 41. The majority (93%) of potassium found in nature is K-39.

Interesting Facts about Potassium:

Potassium chloride (KCl) is sometimes used as a substitute for table salt.

The USDA recommends that adults consume 4.7 grams of potassium per day.

Small amounts of potassium can have a sweet taste. Higher concentrations may have a bitter or salty taste.

Potassium bicarbonate is the chemical name of baking soda. It is used in fire extinguishers, baking powder and antacids.

Some good sources of potassium in our diet include bananas, avocados, nuts, chocolate, parsley, and potatoes.

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