Thorium Th (Element 90) of Periodic Table

90 Th (Thorium)

Appearance:  Silvery, often with black tarnish

Atomic weight:  232.0377

Atomic number (Z):  90

Electrons:  90

Protons:  90

Neutrons:  142

Period:  7

Block:  f

Element category:  Actinide

Electrons per shell:  K2, L8, M18, N32, O18, P10, Q2

Electron configuration:  1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p66d27s2

Phase:  Solid

Melting point: 2023 K (1750 oC)

Boiling point:  5061 K (4788 oC)

Density:  11.7 g/cm3

Half Life (s):  4.43E+17

Lifetime (s):   6.40E+17

Decay mode:  α decay

Neutron cross section (Barns):  7.4

Heat of fusion:  13.81 kJ/mol

Heat of vaporization:  514 kJ/mol

Molar heat capacity:  26.230 J/(mol∙K)

Oxidation states:  4, 3, 2, 1

Ion charge:   Th4+

Electronegativity:  1.3

Valence:  4

Ionisation energies:  1st: 587 kJ/mol   2nd: 1110kJ/mol   3rd: 1930 kJ/mol

Atomic radius:  179.8 pm

Covalent radius:  206±6 pm

Crystal structure:  Face-centred cubic

Sound Speed (thin rod):  2490 m/s

Thermal expansion:  11 μm/(m∙K)

Thermal conductivity: 54 W/(m∙K)

Electrical resistivity:  157 nΩ.m

Magnetic ordering:  Paramagnetic

Volume magnetic susceptibility:  0.0000621

Mass magnetic susceptibility:  53×10-10 m3/kg

Molar magnetic susceptibility:  12.3×10-10 m3/mol

Critical temperature:  1.38 K

Young’s modulus: 79 GPa

Shear modulus:  31 GPa

Bulk modulus:  54 GPa

Poisson ratio:  0.27

Mohs hardness:  3

Molar volume:  19.79 cm3/mol

Vickers hardness:  295-685 MPa

Brinell hardness:  390-1500 MPa

CAS Number:  7440-29-1

Naming:  After Thor

Discovery:  Jöns Jacob Berzelius (1829)

Isotopes:   227Th 228Th 229Th 230Th 231Th 232Th 234Th

Uses:  Thorium is used as an alloying element in magnesium, and  to coat tungsten wire used in electronic equipment, and to control the grain size of plutonium used for electric lamps.

Thorium can be used as a source of nuclear power, India and China are in the process of developing nuclear power plants with thorium reactors.

Thorium oxide is added to glass to create glasses with an high refractive index and low dispersion (For use in High-quality camera lenses), Thorium oxide is also used as an industrial catalyst.

Biological role:  It is toxic due to its radioactivity

Natural abundance:  Thorium is found as the minerals thorite, uranothorite, thorianite and also found in monazite (which is the most important commercial source). Several methods are used to produce the metal, such as reducing thorium oxide with calcium or electrolysis of the fluoride.

World production of thorium exceed 30,00 tones per year.

Abundance 4×10-8%(In Universe), 3×10-8%(In Sun), 3.9×10-6%(In Meteorites), 0.0006%(In Earth crust), 4×10-12%(In Oceans)


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