Name: arsenic
Symbol: As
Atomic number: 33
Atomic weight: 74.92160 (2)
Group in periodic table: 15
Group name: Pnictogen
Period in periodic table: 4
Block in periodic table: p-block
CAS registry ID: 7440-38-2
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).