arsenic

• Description
• General information
• Physical data
• Radii
• Electronegativities
• Solid state structure
• Temperatures
• Enthalpies
• Ionization Enthalpies
• Isotopes
• Further information

Description

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).

General information

Discoveror: Known since ancient times
Date discovered:
Discovered at: not known
Meaning of name: From the Greek word "arsenikon" meaning "yellow orpiment"

Physical data

Standard state: solid at 298 K
Colour: metallic grey
Density of solid at ambient temperature/kg m^-3: 5727
Molar volume/cm³: 12.95

Radii /pm

Atomic: 114
Covalent (single bond):
Pauling radius for the ion [As]^-: 285

Valence shell orbital radius maxima (R_max)

orbital	s	p	d	f
radius	88.5	106.6	25.4	no data

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 2.18
Allred Rochow: 2.20

Crystal Structure

structure: trigonal

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.

Temperatures (/K)

melting point: 1090
boiling point: 887

Enthalpies /kJ mol^-1

fusion: 27.7
vaporization: 32.4

single bond enthalpies:

As-F	As-Cl	As-Br	As-I	As-As
406	322	258	200	382.0

Ionization enthalpies /kJ mol^-1

Number	Enthalpy
1st	944
2nd	1797.8
3rd	2736
4th	4837
5th	6042
6th	12310

Isotopes

This section gives some data for naturally occurring isotopes.

Nominal mass	Accurate mass	% natural abundance
75As	74.9215942 (17)	100

Further Information

• Additional information about WebElements 1.2.2
• This is a licensed copy (here is the full list) of WebElements 1.2.2 and contains a subset of the material contained within the main version of WebElements (version 2)
• For further information please try WebElements version 2
• Sheffield Chemdex: perhaps the largest internet chemistry directory
• Sheffield Chemputer: interactive chemistry calculators on the WWW