Arsenic: the essentials

Elemental arsenic occurs in two solid modifications: yellow, and grey or metallic, with specific gravities of 1.97, and 5.73, respectively. The element is a steel grey, very brittle, crystalline, semimetallic (metalloid) solid. It tarnishes in air, and when heated rapidly oxidises to arsenous oxide which has a garlic odour.

Arsenic and its compounds are poisonous as any reader of "who-done-it" books knows. Upon heating arsenic and some minerals containing arsenic, it sublimes (transfers from the solid to the gaseous state, without passing through the liquid state).

This sample is from The Elements Collection, an attractive and safely packaged collection of the 92 naturally occurring elements that is available for sale.

Arsenic: historical information

Arsenic was discovered by known since ancient times in unknown at not known. Origin of name: from the Greek word "arsenikon" meaning "yellow orpiment".

Arsenic compounds were mined by the early Chinese, Greek and Egyptian civilisations. No doubt they discovered its toxic properties early on.

It is believed that Albertus Magnus obtained the element in 1250 A.D. who obtained it by heating soap together with orpiment (arsenic trisulphide, As2S3).

Arsenic is one of the elements which has an alchemical symbol, shown below (alchemy is an ancient pursuit concerned with, for instance, the transformation of other metals into gold).

{{floatR}}alchemical symbol of arsenic{{/floatR}}

Arsenic around us Read more »

Arsenic, despite its poisonous reputation, may be a necessary ultratrace element for humans. It is a necessary ultratrace element for red algae, chickens, rats, goats, and pigs. A deficiency results in inhibited growth.

Arsenic is found as the free element occasionally, but is found more normally in a number of minerals. Mispickel (arsenopyrite, FeSAs) is the most common mineral. Locations include France, Germany, Italy, Romania, Siberia, and North America.

Abundances for arsenic in a number of different environments. More abundance data »
Location ppb by weight ppb by atoms Links
Universe 8 0.1 Chemical elements abundance by weight in the universe on a miniature periodic table spark table
Crustal rocks 2100 580 Chemical elements abundance by weight in the earth's crust on a miniature periodic table spark table
Human 50 ppb by weight 4 atoms relative to C = 1000000 Chemical elements abundance by weight in humans on a miniature periodic table spark table

Physical properties Read more »

Heat properties Read more »

Crystal structure Read more »

The solid state structure of arsenic is: trigonal.

Arsenic: orbital properties Read more »

Arsenic atoms have 33 electrons and the shell structure is The ground state electronic configuration of neutral Arsenic is [Ar].3d10.4s2.4p3 and the term symbol of Arsenic is 4S3/2.


Isolation: it is not usually necessary to make arsenic in the laboratory as it is commercially available. Arsenic is found in nature in a number of minerals including realgar (As4S4), orpiment (As2S3), arsenolite (As2O3), and iron minerals such as arsenopyrite (FeAsS) and loellingite (FeAs2). Arsenic is made on an industrial scale by heating appropriate minerals in the absence of air. The arsenic is condensed out as a solid.

FeAsS (700°C) → FeS + As(g) → As(s)

Arsenic isotopes Read more »

Table. Stables isotopes of arsenic.
Isotope Mass
(atom %)
spin (I)
moment (μ/μN)
75As 74.9215942 (17) 100 3/2 1.43947

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