|
General |
Name, Symbol, Number | Radium, Ra, 88 |
Series | Alkali earth metals |
Group, Period, Block | 2(IIA), 7 , s |
Density, Hardness | 5000 kg/m3, no data |
Appearance | Silvery white metallic |
Atomic Properties |
Atomic weight | (226.0254) amu |
Atomic radius | 215 pm |
Covalent radius | no data |
van der Waals radius | no data |
Electron configuration | [Rn]7s2 |
e- 's per energy level | 2, 8, 18, 32, 18, 8, 2 |
Oxidation states (Oxide) | 2 (strong base) |
Crystal structure | Cubic body centered |
Physical Properties |
State of matter | solid (nonmagnetic) |
Melting point | 973 K (1292 °F) |
Boiling point | 2010 K (3159 °F) |
Molar volume | 41.09 ×10-3 m3/mol |
Heat of vaporization | no data |
Heat of fusion | 37 kJ/mol |
Vapor pressure | 327 Pa at 973 K |
Speed of sound | no data |
Miscellaneous |
Electronegativity | 0.9 (Pauling scale) |
Specific heat capacity | 94 J/(kg*K) |
Electrical conductivity | no data |
Thermal conductivity | 18.6 W/(m*K) |
1st ionization potential | 509.3 kJ/mol |
2nd ionization potential | 979.0 kJ/mol |
3rd ionization potential | no data |
Most Stable Isotopes |
|
SI units & STP are used except where noted. |
Radium is a
chemical element in the
periodic table that has the symbol Ra and
atomic number 88.
Its appearance is almost pure white, but it blackens with exposure to air. Radium is an
alkaline earth metal
that is found in minute amounts in
uranium ores, and is extremely
radioactive
whose most stable
isotope, Ra-226, has a
half-life of 1602 years and decays into the deadly
radon gas.
Heaviest of the
alkaline earth metals, radium is intensely radioactive and resembles
barium chemically. This metal is found (combined) in minute quantities in the uranium ore
pitchblende, and various other uranium
minerals. Radium preparations are remarkable for maintaining themselves at a higher
temperature than their surroundings, and for their radiations, which are of three kinds:
alpha rays,
beta rays, and
gamma rays. Radium also produces
neutrons when mixed with
beryllium.
When freshly prepared, pure radium metal is brilliant white, but blackens when exposed to air (probably due to nitride[?] formation). Radium is luminescent, decomposes in water and is a bit more volatile than barium.
The only practical uses of radium are derived from its radiative properties. More recently discovered
radioisotopes, such as
cobalt-60 and
cesium-137, are replacing radium in even these limited uses because several of these are much more powerful and others are safer to handle.
- One gram of radium yields ~0.0001 ml of radon gas each day which is used in cancer and other treatments.
- Formerly used in self-luminous paints for watch, clock and instrument dials.
- Neutron source for high energy physics experiments.
Radium (
Latin radius, ray) was discovered by
Marie Curie in
1898 in
pitchblende/
uraninite from North
Bohemia. In
1911 radium was isolated into its pure
metal by Curie and
Andre Debierne[?] through the
electrolysis of a pure radium
chloride solution by using a
mercury cathode and
distilling in an atmosphere of
hydrogen gas.
On February 4, 1936 Radium E became the first radioactive element to be made synthetically.
During the 1930s it was found that worker exposure to radium by handling luminescent paints caused serious health effects which included sores, anemia and bone cancer[?]. This use of radium was stopped soon afterward. Handling of radium has since been blamed for Curie's premature death.
Radium was originally acquired from pitchblende ore from
Joachimsthal, Bohemia[?] (7
metric tons of pitchblende yields 1
gram of radium).
Carnotite[?] sands in
Colorado provide some of the element, but richer ores are found in the
Democratic Republic of the Congo, the
Great Lake area of
Canada and can also be extracted from uranium processing waste. Large uranium deposits are located in
Ontario,
New Mexico,
Utah,
Australia, and in other places.
Isolation (* follow):
(
cathode) Ra
2+* + 2e
- --> Ra (
anode) Cl
-* --> ½Cl
2 (gas|g) + e
-
Its
compounds (which are short lived)
color flames
crimson carmine (rich red or crimson color with a shade of purple) and give a characteristic
spectrum. Due to its very short
half life and intense radioactivity, radium compounds are quite rare occurring almost exclusively in uranium ores.
Radium has 25 different
isotopes, four of which are found in nature, with radium-226 being the most common and stable. Ra-223, Ra-224, Ra-226 and Ra-228 are all generated in the decay of either
U or
Th. Ra-226 is a product of U-238 decay, and is the longest-lived isotope of Ra with a
half-life of 1602 years; next longest is Ra-228, a product of Th-232 breakdown, with a half-life of 6.7 years.
Radium is over 1 million times more radioactive than the same amount of
uranium.
Its decay occurs in at least seven stages; the successive main products have been studied and are called radium emanation or exradio, radium A, radium B, radium C, etc. (The emanation is a heavy gas, the later products are solids.) These products are regarded as unstable elements, each with an atomic weight a little lower than its predecessor.
Radium loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight with lead being a final product of disintegration. The curie is defined as that amount of radioactivity which has the same disintegration rate as 1 gram of Ra-226 (3.7 x 1010 disintegrations per second).
Radium is
poisonous.
Radium is extremely radioactive and its decay product radon is a deadly lung hazard. Since Ra is closely related to calcium, it has the potential for causing great harm by substituting for it in
bone. Inhalation, injection, or body exposure to radium can cause cancer and other body disorders. Stored radium should be ventilated to prevent build-up of radon.
Emitted energy from the decay of radium ionizes gases, affects photographic plates, causes sores on the skin, and produces many other dramatic effects. The degree of activity depends on the proportion of radium present and not whether it is chemically combined.
Lateral Science - Radium Discovery (
http://www.lateralscience.co.uk/radium/RaDisc.html)