Name: radium	Group number: 2
Symbol: Ra	Group name: Alkaline earth metal
Atomic number: 88	Period number: 7
Atomic weight: [ 226 ]	Block: s-block
CAS Registry ID: 7440-14-4	Voice:
Standard state: solid at 298 K	Colour: metallic
Classification: Metallic	Availability:

Radium paint was used in the mid 1900s to paint the hands and numbers of some clocks and watches. The paint was composed of radium salts and a phosphor and glowed in the dark. Image adapted with permission from Prof James Marshall"s (U. North Texas, USA) Walking Tour of the elements CD.

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.

Isolation

All isotopes of radium are radioactive and there is only ever any need to make radium metal on very small scales for research purposes. Radium is extremely scarce but found in uranium ores such as pitchblende at slightly more than 1g in 10 tonnes of ore. It may be made on very small scale by the electrolysis of molten radium chloride, RaCl₂. This was first done using a mercury cathode, which gave radium amalgam. The metal was obtained by distillation away from the amalgam.

cathode: Ra²⁺(l) + 2e^- Raanode: Cl^-(l) ¹/₂Cl₂ (g) + e^-