Introduction group VA

Group VA includes following elements: Nitrogen - [N], Phosphorus - [P], Arsenic - [As], Antimony - [Sb], Bismuth- [Bi].

Nitrogen

Nitrogen is the most abundant uncombined element accessible to man. It comprises 78.1% by volume of the atmosphere (i.e. 78.3 atom% or 75.5 wt%) and is produced industrially from this source on the ultimegatonne scale annually. In combined form it is essential to all forms of life, and constitutes, on average, about 15% by weight of proteins. The industrial fixation of nitrogen for agricultural fertilizers and other chemical products is now carried out on a vast scale in many countries, and the number of moles of anhydrous ammonia manufactured exceeds that of any other compound.

The “discovery” of nitrogen in 1772 is generally credited to Daniel Rutherford, though the gas was also isolated independently about the same time by both C. W. Scheele and H. Cavendish. Rutherford was studying the properties of the residual “air” left after carbonaceous substances were burned in a limited supply of air; he removed the CO2 by means of KOH and so obtained nitrogen which he thought was ordinary air that had taken up phlogiston from the combusted material. The elementary nature of nitrogen was disputed by some even as late as 1840 despite the work of A. L. Lavoisier. The name “nitrogen” was suggested by Jean-Antoine-Claude Chaptal in 1790 when it was realized that the element was a constituent of nitric acid and nitrates.

Compounds of nitrogen have an impressive history. Ammonium chloride was first mentioned in the Historia of Herodotus (fifth century BC) and ammonium salts, together with nitrates, nitric acid and aqua were known to the early alchemists.

Phosphorus

Phosphorus has an extensive and varied chemistry which transcends the traditional boundaries of inorganic chemistry not only because of its propensity to form innumerable covalent “organophosphorus” compounds, but also because of the numerous and crucial roles it plays in the biochemistry of all living things. It was first isolated by the alchemist Hennig Brandt in 1669 by the unsavoury process of allowing urine to putrify for several days before boiling it down to a paste which was then reductively distilled at high temperatures; the vapours were condensed under water to give the element as a white waxy substance that glowed in the dark when exposed to air. Robert Boyle improved the process and in subsequent years made the oxide and phosphoric acid; he referred to the element as “aerial noctiluca”, but the name phosphorus soon became generally accepted. Phosphorus is probably unique among the elements in being isolated first from animal (human) excreta, then from plants, and only a century later being recognized in a mineral.

In much of its chemistry phosphorus stands in relation to nitrogen as sulfur does to oxygen. For example, whereas N2 and O2 are diatomic gases, P and S have many allotropic modifications which reflect the various modes of catenation adopted. Again, the ability of P and S to form multiple bonds to C, N and O, though it exists, is less highly developed than for N, whereas the ability to form extended networks of -P-O-P-O- and -S-O-S-O- bonds is greater; this is well illustrated by comparing the oxides and oxoanions of N and P. "Valency expansion" is another point of difference between the elements of the first and second periods of the periodic table for, although compounds in which N has a formal oxidation state of +5 are known, no simple "single-bonded" species such as NF5 or NCl6- have been prepared, analogous to PF5 and PCl6-. This finds interpretation in the availability of 3d orbitals for bonding in P (and S) but not for N (or O).

Because of the great importance of phosphorus and its compounds in the chemical industry, several books and reviews on their preparation and uses are Some of these applications reflect the fact that P is a vital element for the growth and development of all plants and animals and is therefore an important constituent in many fertilizers. Phosphorus compounds are involved in energy transfer processes (such as photosynthesis, metabolism, nerve function and muscle action), in heredity (via DNA), and in the production of bones and teeth.

Arsenic. Antimony. Bismuth

The three elements arsenic, antimony and bismuth, which complete Group Va of the periodic table, were amongst the earliest elements to be isolated and all were known before either nitrogen (1772) or phosphorus (1669) had been obtained as the free elements. The properties of arsenic sulfide and related compounds have been known to physicians and professional poisoners since the fifth century BC though their use is no longer recommended by either group of practitioners. Isolation of the element is sometimes credited to Albertus Magnus (AD 1193-1280) who heated orpiment (As2S3) with soap, and its name reflects its ancient lineage.

Antimony compounds were also known to the ancients and the black sulfide, stibnite, was used in early biblical times as a cosmetic to darken and beautify women’s eyebrows; a rare Chaldean vase of cast antimony dates from 4000 BC and antimony-coated copper articles were used in Egypt 2500-2200BC. Pliny (~AD 50) gave it the name stibium and writings attributed to Jabir (~AD 800) used the form antimonium; indeed, both names were used for both the element and its sulfide until the end of the eighteenth century. The history of the element, like that of arsenic, is much obscured by the intentionally vague and misleading descriptions of the alchemists, though the elusive Benedictine monk Basil Valentine may have prepared it in 1492 (about the time of Columbus).

Bismuth was known as the metal at least by 1480 though its previous history in the Middle Ages is difficult to unravel because the element was sometimes confused with Pb, Sn, Sb or even Ag. The Gutenberg printing presses (1440 onwards) used type that had been cut from brass or cast from Pb, Sn or Cu, but about 1450 a secret method of casting type from Bi alloys came into use and this particular use is still an important application of the element. The name derives from the German Wismut (possibly white metal or meadow mines) and this was latinized to bisemutum by the sixteenth-century German scientist G. Bauer (Agricola) about 1530. Despite the difficulty of assigning precise dates to discoveries made by alchemists, miners and metal workers, it seems clear that As, Sb and Bi became increasingly recognized in their free form during the thirteenth to fifteenth centuries; they are therefore contemporary with Zn and Co, and predate all other elements except the 7 metals and 2 non-metallic elements known from ancient times (Au, Ag, Cu, Fe, Hg, Pb, Sn; C and S). Arsenic and antimony are classed as metalloids or semi-metals and bismuth is a typical B subgroup (post-transition-element) metal like tin and lead.