TheIUPAC has called itGroup 15 since 1988. Before that, in America it was calledGroup VA, owing to a text by H. C. Deming and theSargent-Welch Scientific Company, while in Europe it was calledGroup VB, which the IUPAC had recommended in 1970.[2] (Pronounced "group five A" and "group five B"; "V" is theRoman numeral 5.) Insemiconductor physics, it is still usually calledGroup V.[3] The "five" ("V") in the historical names comes from the "pentavalency" of nitrogen, reflected by thestoichiometry ofcompounds such asN2O5. They have also been called thepentels.
Like other groups, the members of this family manifest similar patterns inelectron configuration, notably in their valence shells, resulting in trends in chemical behavior.
This group has the defining characteristic whereby each component element has 5 electrons in their valenceshell, that is, 2 electrons in the s sub-shell and 3 unpaired electrons in the p sub-shell. They are therefore 3 electrons shy of filling their valence shell in their non-ionized state. The Russell-Saundersterm symbol of the ground state in all elements in the group is4S3⁄2.
The most important elements of this group to life on Earth arenitrogen (N), which in its diatomic form is the principal component of air, andphosphorus (P), which, like nitrogen, is essential to all known forms of life.
Binary compounds of the group can be referred to collectively aspnictides. Magnetic properties of pnictide compounds span the cases ofdiamagnetic systems (such as BN or GaN) and magnetically ordered systems (MnSb isparamagnetic at elevated temperatures and ferromagnetic at room temperature); the former compounds are usually transparent and the latter metallic. Other pnictides include the ternaryrare-earth (RE) main-group variety of pnictides. These are in the form ofREaMbPnc, where M is acarbon group orboron group element and Pn is any pnictogen except nitrogen. These compounds are betweenionic andcovalent compounds and thus have unusual bonding properties.[4]
These elements are also noted for theirstability in compounds due to their tendency to formcovalentdouble bonds andtriple bonds. This property of these elements leads to their potentialtoxicity, most evident in phosphorus, arsenic, and antimony. When these substances react with various chemicals of the body, they create strongfree radicals that are not easily processed by the liver, where they accumulate. Paradoxically, this same strong bonding causes nitrogen's and bismuth's reduced toxicity (when in molecules), because these strong bonds with other atoms are difficult to split, creating very unreactive molecules. For example,N2, thediatomic form of nitrogen, is used as an inert gas in situations where usingargon or anothernoble gas would be too expensive.
The light pnictogens (nitrogen, phosphorus, and arsenic) tend to form −3 charges when reduced, completing their octet. When oxidized or ionized, pnictogens typically take an oxidation state of +3 (by losing all three p-shell electrons in the valence shell) or +5 (by losing all three p-shell and both s-shell electrons in the valence shell). However heavier pnictogens are more likely to form the +3 oxidation state than lighter ones due to the s-shell electrons becoming more stabilized.[5]
Pnictogens can react withhydrogen to formpnictogen hydrides such asammonia. Going down the group, tophosphane (phosphine),arsane (arsine),stibane (stibine), and finallybismuthane (bismuthine), each pnictogen hydride becomes progressively less stable (more unstable), more toxic, and has a smaller hydrogen-hydrogen angle (from 107.8° in ammonia[6] to 90.48° in bismuthane).[7] (Also, technically, only ammonia and phosphane have the pnictogen in the −3 oxidation state because, for the rest, the pnictogen is less electronegative than hydrogen.)
The +3 oxidation state is bismuth's most common oxidation state because its ability to form the +5 oxidation state is hindered byrelativistic properties on heavier elements, effects that are even more pronounced concerning moscovium. Bismuth(III) formsan oxide,an oxychloride,an oxynitrate, anda sulfide. Moscovium(III) is predicted to behave similarly to bismuth(III). Moscovium is predicted to form all four trihalides, of which all but the trifluoride are predicted to be soluble in water. It is also predicted to form an oxychloride and oxybromide in the +III oxidation state.
Inhydrazine,diphosphane, and organic derivatives of the two, the nitrogen or phosphorus atoms have the −2 oxidation state. Likewise,diimide, which has two nitrogen atoms double-bonded to each other, andits organic derivatives have nitrogen in the oxidation state of −1.
Similarly,realgar has arsenic–arsenic bonds, so the arsenic's oxidation state is +II.
A corresponding compound for antimony is Sb2(C6H5)4, where the antimony's oxidation state is +II.
Antimony tetroxide is amixed-valence compound, where half of the antimony atoms are in the +3 oxidation state, and the other half are in the +5 oxidation state.
It is expected that moscovium will have an inert-pair effect for both the 7s and the 7p1/2 electrons, as thebinding energy of the lone 7p3/2 electron is noticeably lower than that of the 7p1/2 electrons. This is predicted to cause +I to be a common oxidation state for moscovium, although it also occurs to a lesser extent for bismuth and nitrogen.[10]
The pnictogens exemplify the transition from nonmetal to metal going down the periodic table: a gaseous diatomic nonmetal (N), two elements displaying many allotropes of varying conductivities and structures (P and As), and then at least two elements that only form metallic structures in bulk (Sb and Bi; probably Mc as well). All the elements in the group aresolids atroom temperature, except for nitrogen which is gaseous at room temperature. Nitrogen and bismuth, despite both being pnictogens, are very different in their physical properties. For instance, atSTP nitrogen is a transparent non-metallic gas, while bismuth is a silvery-white metal.[11]
Thedensities of the pnictogens increase towards the heavier pnictogens. Nitrogen's density is 0.001251 g/cm3 at STP.[11] Phosphorus's density is 1.82 g/cm3 at STP, arsenic's is 5.72 g/cm3, antimony's is 6.68 g/cm3, and bismuth's is 9.79 g/cm3.[12]
Nitrogen'smelting point is −210 °C and its boiling point is −196 °C. Phosphorus has a melting point of 44 °C and a boiling point of 280 °C. Arsenic is one of only two elements tosublimate at standard pressure; it does this at 603 °C. Antimony's melting point is 631 °C and its boiling point is 1587 °C. Bismuth's melting point is 271 °C and its boiling point is 1564 °C.[12]
All pnictogens up to antimony have at least onestable isotope; bismuth has no stable isotopes, but has a primordialradioisotope with a half-life much longer than the age of the universe (209Bi); and all known isotopes of moscovium are synthetic and highly radioactive. In addition to these isotopes, traces of13N,32P, and33P occur in nature, along with various bismuth isotopes (other than209Bi) in thedecay chains of thorium and uranium.
The nitrogen compoundsal ammoniac (ammonium chloride) has been known since the time of the Ancient Egyptians. In the 1760s two scientists,Henry Cavendish andJoseph Priestley, isolated nitrogen from air, but neither realized the presence of an undiscovered element. It was not until several years later, in 1772, thatDaniel Rutherford realized that the gas was indeed nitrogen.[13]
ThealchemistHennig Brandt first discovered phosphorus in Hamburg in 1669. Brandt produced the element by heating evaporated urine and condensing the resulting phosphorus vapor in water. Brandt initially thought that he had discovered thePhilosopher's Stone, but eventually realized that this was not the case.[13]
Arsenic compounds have been known for at least 5000 years, and the ancient GreekTheophrastus recognized the arsenic minerals calledrealgar andorpiment. Elemental arsenic was discovered in the 13th century byAlbertus Magnus.[13]
Antimony was well known to the ancients. A 5000-year-old vase made of nearly pure antimony exists in theLouvre. Antimony compounds were used in dyes in theBabylonian times. The antimony mineralstibnite may have been a component ofGreek fire.[13]
Bismuth was first discovered by an alchemist in 1400. Within 80 years of bismuth's discovery, it had applications inprinting and decoratedcaskets. TheIncas were also using bismuth in knives by 1500. Bismuth was originally thought to be the same as lead, but in 1753,Claude François Geoffroy proved that bismuth was different from lead.[13]
The term "pnictogen" (or "pnigogen") is derived from theAncient Greek wordπνίγειν (pnígein) meaning "to choke", referring to the choking or stifling property of nitrogen gas.[14] It can also be used as amnemonic for the two most common members, P and N. The term "pnictogen" was suggested by the Dutch chemistAnton Eduard van Arkel in the early 1950s. It is also spelled "pnicogen" or "pnigogen". The term "pnicogen" is rarer than the term "pnictogen", and the ratio of academic research papers using "pnictogen" to those using "pnicogen" is 2.5 to 1.[4] It comes from theGreekrootπνιγ- (choke, strangle), and thus the word "pnictogen" is also a reference to the Dutch and German names for nitrogen (stikstof andStickstoff, respectively, "suffocating substance": i.e., substance in air, unsupportive of breathing). Hence, "pnictogen" could be translated as "suffocation maker". The word "pnictide" also comes from the same root.[14]
The namepentels (from Greekπέντε,pénte, five) also at one time stood for this group.[15]
Nitrogen makes up 25 parts per million of theEarth's crust, 5 parts per million of soil on average, 100 to 500 parts per trillion of seawater, and 78% of dry air. Most nitrogen on Earth is in nitrogen gas, but somenitrate minerals exist. Nitrogen makes up 2.5% of a typical human by weight.[citation needed]
Phosphorus is 0.1% of the earth's crust, making it the 11thmost abundant element. Phosphorus comprises 0.65 parts per million of soil and 15 to 60 parts per billion of seawater. There are 200Mt of accessiblephosphates on earth. Phosphorus makes up 1.1% of a typical human by weight.[13] Phosphorus occurs in minerals of theapatite family, which are the main components of the phosphate rocks.
Arsenic constitutes 1.5 parts per million of the Earth's crust, making it the 53rd most abundant element. The soils hold 1 to 10 parts per million of arsenic, and seawater carries 1.6 parts per billion of arsenic. Arsenic comprises 100 parts per billion of a typical human by weight. Some arsenic exists in elemental form, but most arsenic is found in the arsenic mineralsorpiment,realgar,arsenopyrite, andenargite.[13]
Antimony makes up 0.2 parts per million of the earth's crust, making it the 63rd most abundant element. The soils contain 1 part per million of antimony on average, and seawater contains 300 parts per trillion on average. A typical human has 28 parts per billion of antimony by weight. Some elemental antimony occurs in silver deposits.[13]
Bismuth makes up 48 parts per billion of the earth's crust, making it the 70th most abundant element. The soils contain approximately 0.25 parts per million of bismuth, and seawater contains 400 parts per trillion of bismuth. Bismuth most commonly occurs as the mineralbismuthinite, but bismuth also occurs in elemental form or sulfide ores.[13]
Moscovium is produced several atoms at a time in particle accelerators.[13]
Most arsenic is prepared by heating the mineralarsenopyrite in the presence of air. This formsAs4O6, from which arsenic can be extracted via carbon reduction. However, it is also possible to make metallic arsenic by heating arsenopyrite at 650 to 700 °C without oxygen.[18]
With sulfide ores, the method by which antimony is produced depends on the amount of antimony in the raw ore. If the ore contains 25% to 45% antimony by weight, then crude antimony is produced by smelting the ore in ablast furnace. If the ore contains 45% to 60% antimony by weight, antimony is obtained by heating the ore, also known as liquidation. Ores with more than 60% antimony by weight are chemically displaced with iron shavings from the molten ore, resulting in impure metal.
If an oxide ore of antimony contains less than 30% antimony by weight, the ore is reduced in a blast furnace. If the ore contains closer to 50% antimony by weight, the ore is instead reduced in areverberatory furnace.
Antimony ores with mixed sulfides and oxides are smelted in a blast furnace.[19]
Bismuth minerals do occur, in particular in the form of sulfides and oxides, but it is more economic to produce bismuth as a by-product of the smelting of lead ores or, as in China, of tungsten and zinc ores.[20]
Nitrogen in the form ofammonia is a nutrient critical to most plants' survival.[11]Synthesis of ammonia accounts for about 1–2% of the world's energy consumption and the majority of reduced nitrogen in food.
Nitrogen is a component of molecules critical to life on earth, such asDNA andamino acids.Nitrates occur in some plants, due to bacteria present in the nodes of the plant. This is seen in leguminous plants such as peas[clarification needed] or spinach and lettuce.[citation needed] A typical 70 kg (150 lb) human contains 1.8 kg of nitrogen.[13]
Phosphorus in the form ofphosphates occur in compounds important to life, such as DNA andATP. Humans consume approximately 1 g of phosphorus per day.[24] Phosphorus is found in foods such as fish, liver, turkey, chicken, and eggs. Phosphate deficiency is a problem known ashypophosphatemia. A typical 70 kg human contains 480 g of phosphorus.[13]
Arsenic promotes growth in chickens and rats, and may beessential for humans in small quantities. Arsenic has been shown to be helpful in metabolizing the amino acidarginine. There are 7 mg of arsenic in a typical 70 kg human.[13]
Antimony is not known to have a biological role. Plants take up only trace amounts of antimony. There are approximately 2 mg of antimony in a typical 70 kg human.[13]
Bismuth is not known to have a biological role. Humans ingest on average less than 20 μg of bismuth per day. There is less than 500 μg of bismuth in a typical 70 kg human.[13]
Moscovium is too unstable to occur in nature or have a known biological role. Moscovium does not typically occur in organisms in any meaningful amount.
Nitrogen gas is completelynon-toxic, but breathing in pure nitrogen gas is deadly, because it causesnitrogen asphyxiation.[22] The build-up of nitrogen bubbles in the blood, such as those that may occur duringscuba diving, can cause a condition known as the "bends" (decompression sickness). Many nitrogen compounds such ashydrogen cyanide and nitrogen-basedexplosives are also highly dangerous.[13]
White phosphorus, anallotrope of phosphorus, is toxic, with 1 mg per kg bodyweight being a lethal dose.[11] White phosphorus usually kills humans within a week of ingestion by attacking theliver. Breathing in phosphorus in its gaseous form can cause anindustrial disease called "phossy jaw", which eats away at the jawbone. White phosphorus is also highly flammable. Someorganophosphorus compounds can fatally block certainenzymes in the human body.[13]
Elemental arsenic is toxic, as are many of itsinorganic compounds; however some of its organic compounds can promote growth in chickens.[11] The lethal dose of arsenic for a typical adult is 200 mg and can cause diarrhea, vomiting, colic, dehydration, and coma. Death from arsenic poisoning typically occurs within a day.[13]
Antimony is mildly toxic.[22] Additionally,wine steeped in antimony containers caninduce vomiting.[11] When taken in large doses, antimony causesvomiting in a victim, who then appears to recover before dying several days later. Antimony attaches itself to certain enzymes and is difficult to dislodge.Stibine, or SbH3, is far more toxic than pure antimony.[13]
Bismuth itself is largelynon-toxic, although consuming too much of it can damage the liver. Only one person has ever been reported to have died from bismuth poisoning.[13] However, consumption of soluble bismuth salts can turn a person's gums black.[11]
Moscovium is too unstable to conduct any toxicity chemistry.
^Adachi, S., ed. (2005).Properties of Group-IV, III-V and II-VI Semiconductors. Wiley Series in Materials for Electronic & Optoelectronic Applications. Vol. 15. Hoboken, New Jersey: John Wiley & Sons.Bibcode:2005pgii.book.....A.ISBN978-0-470-09032-9.
^Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.),Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, p. 586,ISBN0-12-352651-5
