Arsenic, Physical and Chemical Properties

Arsenic is a bright silver-gray metalloid; its outermost electrons are not free to move in the crystal structure because they are fixed in position in a covalent bond. It has metallic luster but is brittle with no useful mechanical properties. In addition to the metallic-like form, there are other modifications which change into the metallic-like form above 270°C:

• Black arsenic, formed as a mirror when arsenic hydride is passed through an incandescent glass tube and also when the vapor is rapidly cooled.

• Yellow arsenic, formed by the sudden cooling of arsenic vapor and consists of transparent, waxy crystals. It is unstable and changes into metallic-like arsenic on exposure to light or on gentle heating.

• Brown arsenic, is either a special modification or simply a more finely divided form is obtained in the reduction of solutions of arsenic trioxide in hydrochloric acid with tin(II) chloride or hypophosphorous acid.

Physical Properties

Atomic number	33
Atomic weight	24.92
Relative...