Periodex

General properties

Group

group 15 (pnictogens)

Period

period 4

Category

metalloids

Standard atomic weight

74.921 595(6)

Melting point

1090 K (817 °C)

Boiling point

887 K (614 °C)

Phase at STP

solid

Additional properties

Block

p-block

Electron configuration

[Ar] 3d¹⁰ 4s² 4p³

Electrons per shell

2, 8, 18, 5

Electronegativity

2.18

Density

5.727 g/cm³

Oxidation states

−3, −2, −1, 0, +1, +2, +3, +4, +5 (a mildly oxide)

CAS Number

7440-38-2

Natural isotopes

Discovery history

Discovered by

ancient civilizations

Year of discovery

before 815 CE

Origin of name

The Greek name 'arsenikon' for the yellow pigment orpiment