The Element Potassium
Introduction to Potassium
Potassium, represented with the symbol K, is one of the alkali metals. This element is soft and has a silvery-white color. Just like other alkali metals, potassium mainly takes the form of salts. Additionally, potassium ions are essential for normal nerve transmission inside of living cells.
Ten interesting & fun facts about Potassium
- Potassium was first isolated from potash, plant ashes soaked in a pot with water. The name “potassium” also derives from “potash”.
- The second least dense metal after lithium is potassium.
- The first metal separated by electrolysis was potassium.
- Fats can react with potassium hydroxide to produce soaps.
- Potassium has three main isotopes, and one of the isotopes 40K is radioactive. 40K can be found in all potassium, and is the most common radioisotope in the human body.
- Cells rely on potassium ions to function properly.
- Both potassium deficiency and excess can cause severe symptoms.
- Bananas are a good source of potassium. Five plantains or eleven bananas will supply enough daily amount of potassium. However, too many bananas will also lead to terrifying side effects.
- The commercial extraction of potassium salts is from evaporite deposits in ancient lake bottoms, for example, the Dead Sea.
- Fertilizers use potassium salts as a source of plant nutrition.
Potassium in the Periodic Table
In the periodic table, potassium (K) is in Group 1 and Period 4. It is an alkali metal with atomic number 19. The electron configuration of potassium is [Ar] 4s1. Like other alkali metals, it has a single valence electron that is easily removed, creating a cation. The cationic form of potassium combines with different anions to form salts.
Potassium – Health Effect
Potassium is necessary for the function of living cells because it plays a vital role in the nerve functions and fluid systems of humans. In the nervous system, potassium in its cationic form helps to send messages between the brain and body. These messages are nerve impulses that control heartbeat, muscle contractions, and other body functions. Potassium moving out of the cell, and sodium into the cell creates a change in cell voltage, which in turn creates these nerve impulses. Therefore, getting enough potassium is essential to maintain a healthy nerve function.
People can get potassium from fruits and vegetables, including potatoes, bananas, and white beans; however, it is important that potassium levels stay within a healthy range. Too much potassium in the blood would cause low blood pressure or even a heart attack. Alternatively, potassium deficiency leads to symptoms such as leg cramps, paralysis of muscles, abnormal heartbeat, etc. For those in the low-to-healthy range of potassium, research found that increasing potassium levels will have a significant effect on lowering population blood pressure. In addition, an increase in potassium intake may have direct beneficial effects on the cardiovascular system. The best way of increasing potassium intake is to increase the consumption of fruit and vegetables, which also has beneficial effects on health independent of potassium intake.
Isotopes of Potassium
There are three major isotopes of potassium: 39K, 40K, and 41K. Among them, only 40K is radioactive. In general, a radioactive isotope is one whose nuclei are unstable and can give off energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays.
40K is of great interest to scientists, and it makes up 0.012% of the total amount of potassium found in nature. Potassium is widely distributed in nature, such as in plants, animals, and minerals, which means radioactive 40K exists in most things around us, even in human bodies. However, the amount of it is not enough to cause any harm.
Radioactive 40K in minerals help measure the age of objects. If the mineral contains any potassium, the decay of the 40K will create an isotope of argon, which will be locked up in the mineral. The ratio between 40K and 40Ar, indicates the elapsed time since the mineral formed. The older the rock, the more 40Ar and less 40K it contains.
Potassium Applications in Today’s World
Applied widely in industries and in biological applications, potassium proves its importance.
A Potassium/sodium alloy (NaK) is used as heat exchange media. The strong base potassium hydroxide (KOH) creates soap from fats and oils and is useful in hydrolysis reactions to produce esters. Potassium chlorate (KClO3) is essential in safety matches and is also used in agriculture as an effective weed killer.
Use as Fertilizer
Fertilizers use potassium ionically bonded with chloride, nitrate, and sulfate. It helps to maintain stomata functions (water regulation) in the plant cells and other essential enzymes. Conversely, without potassium, plants are unable to fight against high temperatures. Surprisingly, agricultural fertilizers consume 95% of potash produced, and about 90% of potash comes from KCl.
Potassium Element in Human Body
Potassium is a critical element for the human body. Specifically, potassium ions are present in conjunction with a wide variety of proteins and enzymes. It helps to maintain acidity levels and blood pressure. It is the predominant positive ion inside human cells, sodium being the major positive ions outside human cells. The difference between the concentrations of these two ions inside and outside can make a difference in electric potential, which is essential for basic body functions such as neurotransmission, heart function, and muscle contraction.
History of Potassium
Potassium was the first metal isolated by electrolysis. It was first discovered by Sir Humphry Davy from England in 1807. He found a tiny droplet of liquid metal formed when he applied electrolysis to a small amount of melted potash, and he named the element “potassium” based on the word “potash”.
Potassium Chemistry – compounds, reactions, oxidation states
Chemical Properties of Potassium
Just like other alkali metals, potassium is very reactive. It can react with water violently to produce hydrogen (H2) gas. The excessive heat generated by this reaction, together with the H2 as a product, can be explosive. Potassium can also react with air and form oxide layers. When potassium is burned in the air, it can form the orange potassium superoxide in the form of KO2. Potassium can also react rapidly with all the halogens (F2, Cl2, I2) to form potassium halides (KF, KCl, KBr).
Potassium chloride (KCl) is the most important compound of potassium. Artificial fertilizers make the most use of this compound. It is odorless, has a white/colorless crystal look, and can dissolve in water readily. Other potassium compounds are also commercially important:
- K2SO4: Potassium Sulfate is a white and hard crystal. It is non-flammable and soluble in water but not in alcohol. It also serves as a fertilizer, which helps plants grow better.
- KHCO3: Baking soda, or potassium bicarbonate can be used as baking powders, antacid (for upset stomach), and additives in soft drinks.
- KHSO3: Potassium bisulfite is used in food preservation, bleaching of textiles, and tanning of leathers. Potassium bisulfite is a chemical mixture with the approximate chemical formula of KHSO3. It is not an actual compound but a mixture of salts that give solutions composed of potassium ions and bisulfite.
- KBr: Potassium bromate is used in engraving and as a bread additive. It is a white crystal and is soluble in water. In a dilute aqueous solution, potassium bromide tastes sweet. At higher concentrations, it doesn’t taste very pleasant.
- K2SiF6: Potassium fluorosilicate is used for specialized glasses and ceramics.
- KOH: Potassium hydroxide, also called caustic potash, has many industrial applications including paint remover, manufacturing of specialized soaps, fuel cells, and batteries. Additionally, like NaOH, it serves as a source of OH–, a highly nucleophilic anion that attacks polar bonds in organic materials.
- KNO3: Potassium nitrate is present in explosives, fireworks, matches, and rocket fuel.
Isolation of Potassium
Potassium salts reside in evaporite deposits in ancient lake bottoms and seabeds. The extraction of potassium salts from these extensive sources is economically friendly. The basic potassium source types are the carnallites, containing 45-85% carnallite and 18-50% halite with small amounts of sylvite, anhydrite, clay minerals, and carbonates; sylvinite including 95–98% sylvite and halite, the remainder being an insoluble residue; and hard salt, containing 8–25% sylvite, 18–30% kieserite, 40–60% halite, and 0.5–2.0% carbonates, anhydrite, and clay minerals. The majority of the known resources are concentrated in the USSR in the Urals (Solikamsk, Perm Oblast), western Kazakhstan, western Ukraine, and Byelorussia. Significant foreign deposits include those in the German Democratic Republic (Stassfurt), the Federal Republic of Germany (Hanover, the Harz, Hesse, Baden), the USA (the Carlsbad region in New Mexico; Lake Searles in California), Canada (Saskatchewan), France (Alsace), and Italy (Sicily).
Several methods can be applied to separate potassium salts from Na- and Mn-compounds. Particularly, fractional precipitation is a widely used method to isolate these soluble salts. And most of the potassium is acquired in the form of Potassium Chloride (KCl) and used as fertilizer.
First Isolation Method
Sir Humphry Davy first isolated pure potassium through a simple lab-based chemistry experiment in 1807. More specifically, he applied electricity to melted wood ashes in a process called electrolysis. In the electrolysis of wood ash, a solution is first prepared by placing the wood ash into a metal dish and heating the ash with a Bunsen burner. The ash, containing a high concentration of potassium hydroxide (KOH), will melt. Then, a wire attaches to each electrode of a battery, and the battery leads are placed into the molten ash until liquid potassium metal forms near the anode. The wire on the positive terminal serves as the anode, and the wire on the negative terminal is the cathode. At the anode, potassium metal accumulates.
This electrolysis process was also used in industries in the 1920s. However, the thermal process of reacting sodium with potassium chloride in a chemical equilibrium reaction became the dominant industrial method.
Potassium oxidation states
The electron configuration of potassium is [Ar]4s1. The most common oxidation state is K+1.
Physical properties of Potassium
Potassium is a soft alkali metal with a color of silvery-white. It can react with water and oxygen.
- Potassium Symbol: K
- Atomic Number: 19
- Atomic Mass: 39.0983 amu
- Melting point: 312.46 K
- Boiling point: 961 K
- Density: 1.53 g/cm3
- Electronegativity: 0.8
- Ionization Energy: 4.341 eV
- Oxidation State: +1
- Classification: Alkali metal, Group I metal
- The natural abundance of 2.6% in the earth’s crust
- Electron shell configuration: [Ar]4s1
- Isotopes – Potassium has 3 main isotopes: 39K, 40K, 41K
Where can I buy Potassium?
Regular chemical suppliers sell Potassium. Price changes depending on purity (usually $2 – $5/g). Lower purity of potassium metal is cheaper. However, the long-term storage of potassium metal is complex. Dry non-reactive gas or mineral oil surrounds the element to prevent the formation of a potassium superoxide layer.
In addition, because potassium is essential for human health, most general stores sell potassium for people who do not have enough potassium in their daily diet or have potassium deficiency because of illness.