Periodic Table


Atomic number: 88
Atomic weight: 226
Symbol: Ra
Group number: 2
Electronic configuration: [Rn].7s2


Pure metallic radium is brilliant white when freshly prepared, but blackens on exposure to air, probably due to formation of the nitride. It exhibits luminescence, as do its salts; it decomposes in water and is somewhat more volatile than barium. Radium imparts a carmine red colour to a flame.

Radium emits a, b, and g rays and when mixed with beryllium produces neutrons. Inhalation, injection, or body exposure to radium can cause cancer and other body disorders. alkaline earth metal, white but tarnishes black upon exposure to air, luminesces, decomposes in water, emits radioactive radon gas, disintegrated radioactively until it reaches stable lead, radiological hazard, a, b, and g emitter, exposure to radium can cause cancer and other body disorders. Radium is over a million times more radioactive than the same mass of uranium.

General information

Discoveror: Pierre and Marie Curie
Date discovered: 1898
Discovered at: France
Meaning of name: From the Latin word "radius" meaning "ray"

Physical data

Standard state: solid at 298 K
Colour: metallic
Density of solid at ambient temperature/kg m-3: 5000
Molar volume/cm3: 41.09

Radii /pm

Atomic: no data
Covalent (single bond):
Pauling radius for the ion [Ra]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius251.2no datano datano data


Both values are quoted on the Pauling scale.

Pauling: 0.9
Allred Rochow: 0.97

Crystal Structure

structure: bcc (body-centred cubic)

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: 973
boiling point: 2010

Enthalpies /kJ mol-1

fusion: 8.4
vaporization: 125

single bond enthalpies:
Ra-F Ra-Cl Ra-Br Ra-I Ra-Ra
no data no data no data no data no data

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Ra.html