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Radium

(226)

Name: Radium
Symbol: Ra
Atomic number: 88
Atomic weight: (226)
CAS Registry ID: 7440-14-4

Group name: Alkaline earth metal
Period number: 7
Block: s-block
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Description

Radium is an alkaline earth metal that is a silvery white color in its natural solid state. It oxidizes easily in air, and it is extremely radioactive. Radium has an atomic weight of 226, a melting point of 1292 °F, and a boiling point of 3159 °F. Radium used to be used for many commercial purposes in the form of self-luminous paints; once the toxic traits of radium were discovered these uses were quickly stopped. Now, radium is only used for physics experiments and in cancer therapies.

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Isolation

This element is hardly ever synthesized or isolated anymore due to the extreme dangers that it presents. However, there are methods that can be used to synthesize or isolate radium from its sources.

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Radium is formed as a product of uranium decay, and so it is found in all ores which also contain uranium. When radium was used commercially for luminous paints, it was extracted from pitchblende ores and from rich uranium deposits. Pitchblende is also called uraninite, and it contains high amounts of uranium in addition to lead and rare earth elements. The isolation process involved reducing the radium in the pitchblende down to radium chloride. The radium chloride was reduced using electrolysis of the molten ore through a mercury cathode into a radium amalgam. Further distillation processes removed the chlorine to yield pure radium. Radium is also extracted from waste that is produced from uranium processing. Radium is never isolated on a small scale laboratory basis as it is so dangerous. Decaying stored isolated radium can also produce hazardous radon gases, and so the storage and handling of this element cannot be taken lightly.

General
Name	Radium
Symbol	Ra
Number	88
Chemical series	alkaline earth metals
Group	2
Period	7
Block	s
Appearance	silvery white metallic
Standard atomic weight	(226) g·mol⁻¹
Electron configuration	[Rn] 7s²
Electrons per shell	2, 8, 18, 32, 18, 8, 2

Atomic properties
Crystal structure	cubic body centered
Oxidation states	2 (strongly basic oxide)
Electronegativity	0.9 (scale Pauling)
Ionization energies	1st: 509.3 kJ/mol
(more)	2nd: 979.0 kJ/mol
(more)
Atomic radius	215 pm
Atomic radius (calc.)
Covalent radius
Van der Waals radius

Physical properties
Phase	solid
Density (near r.t.)	5.5 g·cm⁻³
Liquid density at m.p.
Melting point	973 K (700 °C, 1292 °F)
Boiling point	2010 K (1737 °C, 3159 °F)
Critical point
Heat of fusion	8.5 kJ·mol⁻¹
Heat of vaporization	113 kJ·mol⁻¹
Heat capacity

Miscellaneous
Magnetic ordering	nonmagnetic
Electrical resistivity	(20 °C) 1 µ Ω·m
Thermal conductivity	(300 K) 18.6 W·m⁻¹·K⁻¹
Thermal expansion
Speed of sound (thin rod)
Young's modulus
Shear modulus
Bulk modulus
Poisson ratio
Mohs hardness
Vickers hardness
Brinell hardness
CAS registry number	7440-14-4

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Radium

Description

Isolation

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