Atomic number: 33

Symbol: As

Category: metalloid

Density at 25°C: solid:  5.727 g·cm−3

Arsenic is perhaps best known as a toxin to most life. But it does have its uses particularly in semi conductors for electronic circuits. The use of arsenic is being reduced due to its toxicity in water ways. 


Arsenic crystals. image: wikipedia

Use, natural applications or common combinations: 

  • Car batteries - Lead components strengthened by the presence of a few percent of arsenic.
  • Insecticides (though banned in many places)
  • Found in treated woods for building - treatment of wood with chromated copper arsenate (CCA).

Basic characteristics:

  • Standard atomic weight: 74.921 60(2)
  • Melting point: 938.25 °C
  • Boiling point: doesn't really melt but sublimes at 615 °C
  • Radioactivity:  all stable naturally
    • arsenic-74 (a positron emitter) may have uses as a medical tracer