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Arsenic is a poisonous metalloid first discussed by Albertus Magnus in 1250, and was first synthesized by Murray Mickiewicz & Stanley Bruce Wild in 1976. Arsenic is a chemical element with the symbol As and atomic number of 33, which means it has 33 protons & electrons. Arsenic also has an atomic weight of 74.92 and tends to be found in a solid state of matter. You can find Arsenic in Group 15 (P-Block) and in Period 4.


Arsenic has 23 isotopes whose half-lives are known, with mass numbers 65 to 87. Of these, only one is stable: 75As. The number of neutrons in the most abundant isotope is 42.

Arsenic is typically a gray color. It has a metallic sheen and conducts electricity. Yellow arsenic is metastable, is a poor electrical conductor and does not have a metallic sheen. It is prepared by cooling gray arsenic vapor in liquid air. It reverts to gray arsenic at room temperature.. Black arsenic can be prepared by cooling arsenic vapor at 100oC – 200 oC. It is glassy, brittle and a poor electrical conductor.

Most arsenic is obtained as a by-product of processing gold, silver, copper, and other metal ores.


Wood preservation, Insecticides, (GaAs) Laser Diodes & LEDS, Lead Alloys for Ammunition (less than 2%).

Harmful Effects

Arsenic is immediately dangerous to life or health at 5 mg m-3. Our bodies do not readily absorb the element itself, hence pure arsenic is much less dangerous than As(III) compounds such as AsH3 and As2O3 which are absorbed easily and are carcinogenic with high toxicity.

Name Arsenic
Atomic Number 33
Atomic Weight 74.92
Symbol As
Melting Point ( °C ) 817 degrees C, 1090 K
Boiling Point ( °C ) 603 degrees C, 876 K
Density (g/cm3) 5.776 grams per cubic centimeter
Earth crust (%) 0.00021%
Discovery (Year) 1250 by Albertus Magnus
Group 15 (P-Block)
Electron configuration 4s2 3d10 4p3
Ionization energy (eV) 9,7886

References: http://www.chemicool.com/elements/arsenic.html