Potassium is a soft, metallic-white, slightly bluish alkali metal that is naturally found bound to other elements in seawater and in many minerals. It oxidizes quickly on contact with air and reacts violently with water. It chemically resembles sodium.
In the periodic table, potassium is one of the alkali metals. All alkali metals have one valence electron in the outer shell, which is easily released to form a positively charged ion – a cation, which when combined with anions forms a salt. Potassium in nature is found only in ionic salts. Elemental potassium is a soft, silvery-white, alkaline metal that oxidizes rapidly in air and reacts violently with water, producing enough heat to ignite the hydrogen emitted in the reaction and burns with a purple flame. It is found dissolved in seawater (i.e. 0.04% potassium by weight), and is part of many minerals.
Potassium is chemically very similar to sodium, the preceding element in Group 1 of the periodic table. They have the same first ionization energy, which allows each atom to release its only outer electron. That they were different elements that combine with the same anions to make similar salts was suspected in 1702, and was proved in 1807 using electrolysis. Natural potassium consists of three isotopes, one of which, K is radioactive. Traces of K are found in all potassium, and it is the most common radioisotope in the human body.
Potassium ions are necessary for the function of all living cells. Transfer of K ions through nerve cell membranes is necessary for normal nerve transmission; Deficiency and excess of potassium can each result in many abnormalities, including abnormal heart rhythms and various electrocardiography abnormalities. Fresh fruit and vegetables are good sources of potassium. The body responds to the intake of dietary potassium, which increases serum potassium levels, by shifting potassium from outside into cells and increasing the excretion of potassium by the kidneys.
- Atomic Number of Potassium Potassium is a chemical element with atomic number 19 which means there are 19 protons and 19 electrons in the atomic structure. The chemical symbol for Potassium is K.
- Atomic Number of Potassium Atomic Number of Potassium is 19. Chemical symbol for Potassium is K. Number of protons in Potassium is 19. Atomic weight of Potassium is 39.0983 u or g/mol. Melting point of Potassium is 63,7 °C and its the boiling point is 774 °C.
- Potassium is element number 19. This means the atomic number of potassium is.
- Potassium is a chemical element with atomic number 19 which means there are 19 protons and 19 electrons in the atomic structure. The chemical symbol for Potassium is K. Potassium was first isolated from potash, the ashes of plants, from which its name derives.
Read also: Foods Rich in Potassium (Kalium) | What Foods With Potassium in Them? Good For Heart And Bones
The name is derived from the english word potash. The chemical symbol K comes from kalium, the Mediaeval Latin for potash, which may have derived from the arabic word qali, meaning alkali. Potassium is a soft, silvery-white metal, member of the alkali group of the periodic chart.
Most of the industrial applications, they exploit the high solubility of K compounds in water, such as K soap. Heavy crop production quickly depletes soil potassium, and this can be overcome with fertilizers containing potassium, which constitute 95% of global potassium production.
Health
Benefits
It is one of the most important minerals in the body. It helps regulate fluid balance, muscle contractions and nerve signals. What’s more, a high-potassium diet may help reduce blood pressure and water retention, protect against stroke and prevent osteoporosis and kidney stones.
They assist in a range of essential body functions, including:
- blood pressure
- normal water balance
- muscle contractions
- nerve impulses
- digestion
- heart rhythm
- pH balance (acidity and alkalinity)
Deficiency
Certain conditions can cause deficiencies, or hypokalemia. These include:
- kidney disease
- overuse of diuretics
- excessive sweating, diarrhea, and vomiting
- magnesium deficiency
- use of antibiotics, such as carbenicillin and penicillin
The symptoms of hypokalemia are different depending on how severe your deficiency is.
A temporary decrease in potassium may not cause any symptoms. For example, if you sweat a lot from a hard workout, your potassium levels may normalize after eating a meal or drinking electrolytes before any damage is done.
However, severe deficiencies can be life-threatening. Signs of deficiency include:
- extreme fatigue
- muscle spasms, weakness, or cramping
- irregular heartbeat
- constipation, nausea, or vomiting
Hypokalemia is usually diagnosed with a blood test. Your doctor may also order an electrocardiogram of your heart and an arterial blood gas test to measure pH levels in your body.
Overdose
Too much of it can cause hyperkalemia. This is rare in people who eat balanced diets. Risk factors for overdose include:
- taking too many potassium supplements
- kidney disease
- prolonged exercise
- cocaine use
- potassium-conserving diuretics
- chemotherapy
- diabetes
- severe burns
The most obvious symptom of too much of it is an abnormal heartbeat (arrhythmia). Severe cases can lead to death. People with mild cases of high potassium rarely have noticeable symptoms. Your doctor should order occasional blood work if you have any risk factors.
Potassium in the periodic table
| Atomic number (Z) | 19 |
|---|---|
| Group | group 1: H and alkali metals |
| Period | period 4 |
| Block | s-block |
| Electron configuration | [Ar] 4s1 |
| Electrons per shell | 2, 8, 8, 1 |
Physical properties
| Physical properties | |
|---|---|
| Phase at STP | solid |
| Melting point | 336.7 K (63.5 °C, 146.3 °F) |
| Boiling point | 1032 K (759 °C, 1398 °F) |
| Density (near r.t.) | 0.89 g/cm3 |
| when liquid (at m.p.) | 0.828 g/cm3 |
| Critical point | 2223 K, 16 MPa |
| Heat of fusion | 2.33 kJ/mol |
| Heat of vaporization | 76.9 kJ/mol |
| Molar heat capacity | 29.6 J/(mol·K) |
Atomic properties
| Atomic properties | |
|---|---|
| Oxidation states | −1, +1 (a strongly basic oxide) |
| Electronegativity | Pauling scale: 0.82 |
| Ionization energies | |
| Atomic radius | empirical: 227 pm |
| Covalent radius | 203±12 pm |
| Van der Waals radius | 275 pm |
| Atomic radius, non-bonded (Å) | 2.75 | Covalent radius (Å) | 2.00 |
| Electron affinity (kJ mol−1) | 48.385 | Electronegativity (Pauling scale) | 0.82 |
| Ionisation energies (kJ mol−1) | 418.81 3051.83 4419.607 5876.92 7975.48 9590.6 11342.82 14943.65 | ||
Other properties
| Other properties | |
|---|---|
| Natural occurrence | primordial |
| Crystal structure | body-centered cubic (bcc) |
| Speed of sound thin rod | 2000 m/s (at 20 °C) |
| Thermal expansion | 83.3 µm/(m·K) (at 25 °C) |
| Thermal conductivity | 102.5 W/(m·K) |
| Electrical resistivity | 72 nΩ·m (at 20 °C) |
| Magnetic ordering | paramagnetic |
| Magnetic susceptibility | +20.8·10−6 cm3/mol (298 K) |
| Young’s modulus | 3.53 GPa |
| Shear modulus | 1.3 GPa |
| Bulk modulus | 3.1 GPa |
| Mohs hardness | 0.4 |
| Brinell hardness | 0.363 MPa |
| CAS Number | 7440-09-7 |
History
| History | |
|---|---|
| Discovery and first isolation | Humphry Davy (1807) |
Isotopes
Potassium (K) has 24 known isotopes with mass numbers varying between 32 and 55, as well as four nuclear isomers. K occurs in nature in the form of three isotopes: 39K (majority) and 41K, both stable, and a long-lived radioisotope (half-life of 1.248 billion years), 40K. Its standard atomic mass is 39.0983 (1) u. The other potassium radioisotopes all have a half-life of less than one day, and most of them less than one minute.
| Main isotopes | |||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||||||||||
Periodic Table of Elements | Complete List of Chemical Elements by Group, Name, Symbol, Color and Type
Sources: Royal Society of Chemistry,
Photo credit: Wikimedia Commons
Photo explanations: pieces of potassium metal. Cut Potassium pieces from Dennis s.k collection.
Potassium Atomic Number 19
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Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work!Potassium (K), chemical element of Group 1 (Ia) of the periodic table, the alkali metalgroup, indispensable for both plant and animal life. Potassium was the first metal to be isolated by electrolysis, by the English chemist Sir Humphry Davy, when he obtained the element (1807) by decomposing molten potassium hydroxide (KOH) with a voltaic battery.
| atomic number | 19 |
|---|---|
| atomic weight | 39.098 |
| melting point | 63.28 °C (145.90 °F) |
| boiling point | 760 °C (1,400 °F) |
| specific gravity | 0.862 (at 20 °C, or 68 °F) |
| oxidation states | +1, −1 (rare) |
| electron configuration | 2-8-8-1 or 1s22s22p63s23p64s1 |
Properties, occurrence, and uses
Potassium metal is soft and white with a silvery lustre, has a low melting point, and is a good conductor of heat and electricity. Potassium imparts a lavender colour to a flame, and its vapour is green. It is the seventh most abundant element in Earth’s crust, constituting 2.6 percent of its mass.
The potassium content of the Dead Sea is estimated at approximately 1.7 percent potassium chloride, and many other salty bodies of water are rich in potassium. The waste liquors from certain saltworks may contain up to 40 grams per litre of potassium chloride and are used as a source of potassium.
Potassium Atomic Number Iron
Most potassium is present in igneous rocks, shale, and sediment in minerals such as muscovite and orthoclasefeldspar that are insoluble in water; this makes potassium difficult to obtain. As a result, most commercial potassium compounds (often loosely called potash) are obtained via electrolysis from soluble potassium compounds, such as carnallite (KMgCl3∙6H2O), sylvite (potassium chloride, KCl), polyhalite (K2Ca2Mg[SO4]4∙2H2O), and langbeinite (K2Mg2[SO4]3), which are found in ancient lake beds and seabeds.
Potassium Atomic Number Of Neutrons
Potassium is produced by sodium reduction of molten potassium chloride, KCl, at 870 °C (1,600 °F). Molten KCl is continuously fed into a packed distillation column while sodium vapour is passed up through the column. By condensation of the more volatile potassium at the top of the distillation tower, the reaction Na + KCl → K + NaCl is forced to the right. Efforts to devise a scheme for commercial electrolytic production of potassium have been unsuccessful because there are few salt additives that can reduce the melting point of potassium chloride to temperatures where electrolysis is efficient.
There is little commercial demand for potassium metal itself, and most of it is converted by direct combustion in dry air to potassium superoxide, KO2, which is used in respiratory equipment because it liberates oxygen and removes carbon dioxide and water vapour. (The superoxide of potassium is a yellow solid consisting of K+and O2− ions. It also can be formed by oxidation of potassium amalgam with dry air or oxygen.) The metal is also used as an alloy with sodium as a liquid metallic heat-transfer medium. Potassium reacts very vigorously with water, liberating hydrogen (which ignites) and forming a solution of potassium hydroxide, KOH.
Sodium-potassium alloy (NaK) is used to a limited extent as a heat-transfer coolant in some fast-breeder nuclear reactors and experimentally in gas-turbine power plants. The alloy is also used as a catalyst or reducing agent in organic synthesis.
In addition to the alloys of potassium with lithium and sodium, alloys with other alkali metals are known. Complete miscibility exists in the potassium-rubidium and potassium-cesium binary systems. The latter system forms an alloy melting at approximately −38 °C (−36 °F). Modification of the system by the addition of sodium results in a ternary eutectic melting at approximately −78 °C (−108 °F). The composition of this alloy is 3 percent sodium, 24 percent potassium, and 73 percent cesium. Potassium is essentially immiscible with all the alkaline-earth metals, as well as with zinc, aluminum, and cadmium.
Potassium (as K+) is required by all plants and animals. Plants need it for photosynthesis, regulation of osmosis and growth, and enzyme activation. Every animal has a closely maintained potassium level and a relatively fixed potassium-sodium ratio. Potassium is the primary inorganic cation within the living cell, and sodium is the most abundant cation in extracellular fluids. In higher animals, selective complexants for Na+ and K+ act at cellmembranes to provide “active transport.” This active transport transmits electrochemical impulses in nerve and muscle fibres and in balancing the activity of nutrient intake and waste removal from cells. Too little or too much potassium in the body is fatal; however, potassium in the soil ensures the presence of this indispensable element in food.
The potassium content of plants varies considerably, though it is ordinarily in the range of 0.5–2 percent of the dry weight. In humans the ratio of potassium between the cell and plasma is approximately 27:1. The potassium content of muscle tissue is approximately 0.3 percent, whereas that of blood serum is about 0.01–0.02 percent. The dietary requirement for normal growth is approximately 3.3 grams (0.12 ounce) of potassium per day, but the ingestion of more than 20 grams (0.7 ounce) of potassium results in distinct physiological effects. Excess potassium is excreted in the urine, and a significant quantity may be lost during sweating.
Natural potassium consists of three isotopes: potassium-39 (93.26 percent), potassium-41 (6.73 percent), and radioactive potassium-40 (about 0.01 percent); several artificial isotopes have also been prepared. Potassium-39 is normally about 13.5 times more plentiful than potassium-41. The natural radioactivity of potassium is due to beta radiation from the potassium-40 isotope (109 years half-life). The disintegration of potassium-40 is used in geological age calculations (seepotassium-argon dating). Potassium easily loses the single 4selectron, so it normally has an oxidation state of +1 in its compounds, although compounds that contain the anion, K−, can also be made.
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