Page 23 - Curriculum Visions Dynamic Book

Arsenic (As)
Element 33.A metalloid in group 5 (the nitrogen group) in the Periodic Table.
It is common in nature as compounds and occasionally in grey and yellow elemental form. Grey arsenic is very brittle and rapidly tarnishes in air; the yellow form is softer.
Arsenic sublimes, changing from solid to vapour and back to solid again without the intervening liquid phase.Arsenic is well known as a poison.The smell of arsenic vapour resembles garlic.
Discovery
Arsenic has been known since ancient times. It was mined by all ancient civilisations, probably for use as a poison.
Technology
Arsenic oxide is used
as a pesticide (poison),
in adhesives, and as a decolouriser in glassmaking. It is also used in the doping of silicon in making integrated circuits. It can be used to make lead shot harder and also in fireworks to produce colour.
Geology
The native form of arsenic only appears
very occasionally. It is most usually found
as a sulphide – realgar (As4S4), orpiment (As2S3) – or as the oxide arsenolite (As2O3), and in iron sulphide minerals such as mispickel or arsenpyrite (FeAsS).
Biology
Although arsenic is poisonous to both plants and animals in large doses, it is an essential microelement for some
algae and in many animals. Without trace amounts
of arsenic, growth is stunted.
 Bright yellow orpiment crystals with red realgar veins.
Both minerals contain arsenic.
Key facts...
Name: arsenic
Symbol: As
Atomic number: 33
Atomic weight: 74.92
Position in Periodic Table: group 5 (15) (nitrogen
group); period 4
State at room temperature: solid
Colour: metallic grey or yellow
Density of solid: 5.7 g/cc
Melting point: 817°C
Boiling point: n/a
Origin of name: from the Greek word arsenikon,
meaning yellow orpiment
Shell pattern of electrons: 2–8–18–5
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