Arsenic compounds

Compounds of arsenic resemble in some respects those of phosphorus which occupies the same group (column) of the periodic table.

[1] In the +3 oxidation state, arsenic is typically pyramidal owing to the influence of the lone pair of electrons.

[4] It oxidises readily in air to form arsenic trioxide and water, and analogous reactions take place with sulfur and selenium instead of oxygen.

[10] The valence electron count of GaAs is the same as a pair of Si atoms, but the band structure is completely different which results in distinct bulk properties.

[13][14][15] Cacodylic acid, which is of historic and practical interest, arises from the methylation of arsenic trioxide, a reaction that has no analogy in phosphorus chemistry.

Cacodyl was the first organometallic compound known (even though arsenic is not a true metal) and was named from the Greek κακωδία "stink" for its offensive odor; it is very poisonous.