Thulium

Thulium is a chemical element that has the symbol Tm and atomic number 69. A lanthanide element, thulium is the least abundant of the rare earths. It is an easily workable metal with a bright silvery-gray luster and can be cut by a knife. It has some corrosion resistance in dry air and good ductility. Naturally occurring thulium is made entirely of the stable isotope Tm-169.
General | |||||||||||||||
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Name, Symbol, Number | thulium, Tm, 69 | ||||||||||||||
Chemical series | lanthanides | ||||||||||||||
Group, Period, Block | n/a, 6, f | ||||||||||||||
Appearance | silvery gray |
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Standard atomic weight | 168.93421(2) g·mol-1 | ||||||||||||||
Electrons per shell | 2, 8, 18, 31, 8, 2 | ||||||||||||||
Physical properties | |||||||||||||||
Phase | solid | ||||||||||||||
Density (near r.t.) | 9.32 g·cm−3 | ||||||||||||||
Liquid density at m.p. | 8.56 g·cm−3 | ||||||||||||||
Melting point | 1818K (1545°C, 2813°F) |
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Boiling point | 2223K (1950°C, 3542°F) |
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Heat of fusion | 16.84 kJ·mol-1 | ||||||||||||||
Heat of vaporization | 247 kJ·mol-1 | ||||||||||||||
Heat capacity | (25°C) 27.03 J·mol-1·K-1 | ||||||||||||||
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Atomic properties | |||||||||||||||
Crystal structure | hexagonal | ||||||||||||||
Oxidation states | 3 (basic oxide) |
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Electronegativity | 1.25 (Pauling scale) | ||||||||||||||
Ionization energies (more) |
1st: 596.7 kJ·mol-1 | ||||||||||||||
2nd: 1160 kJ·mol-1 | |||||||||||||||
3rd: 2285 kJ·mol-1 | |||||||||||||||
Atomic radius | 175 pm | ||||||||||||||
Atomic radius (calc.) | 222 pm | ||||||||||||||
Miscellaneous | |||||||||||||||
Magnetic ordering | no data | ||||||||||||||
Electrical resistivity | (r.t.) (poly) 676 nΩ·m | ||||||||||||||
Thermal conductivity | (300K) 16.9 W·m-1·K-1 | ||||||||||||||
Thermal expansion | (r.t.) (poly) 13.3 µm/(m·K) |
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Young's modulus | 74.0 GPa | ||||||||||||||
Shear modulus | 30.5 GPa | ||||||||||||||
Bulk modulus | 44.5 GPa | ||||||||||||||
Poisson ratio | 0.213 | ||||||||||||||
Vickers hardness | 520 MPa | ||||||||||||||
Brinell hardness | 471 MPa | ||||||||||||||
CAS registry number | 7440-30-4 |

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