76OsOsmium

Osmium (from Ancient Greek ὀσμή (osmḗ) 'smell') is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element. When experimentally measured using X-ray crystallography, it has a density of 22. 59 g/cm3. Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness. Osmium is among the rarest elements in the Earth's crust, making up only 50 parts per trillion (ppt). It is estimated to be about 0. 6 parts per billion in the universe and is therefore the rarest precious metal.

Atomic properties

Standard atomic weight	190.23 ±0.03
Atomic mass	190.233 u

Atomic radii

Radius (empirical)	135 pm
Radius (calculated)	185 pm
Covalent radius	144 ±4 pm

Atomic shell

Electron configuration	Xe 4f¹⁴ 5d⁶ 6s²
Ionization energy	(1^st) 8.43823 eV (2^nd) 17 eV (3^rd) 25 eV (4^th) 41 eV (5^th) 55 eV
Shell model	Electrons k-shell:2 l-shell:8 m-shell:18 n-shell:32 o-shell:14 p-shell:2

Physical properties

Phase	solid
Density	22.59 g·cm⁻³
Molar volume	8.42·10^-6 m³·mol⁻¹
Speed of sound	4,940 m·s⁻¹ (293.1 K)

Temperatures

Melting point	3,306 K
Boiling point	5,285 K
Liquid range	1,979 K
Transition temperature	0.7 K

Enthalpies

Melting enthalpy	31 kJ·mol^-1
Enthalpy of vaporization	630 kJ·mol^-1
Binding energy	789 kJ·mol^-1

Heat and conductivity

Specific heat capacity	130 J·kg⁻¹·K⁻¹
Thermal conductivity	88 W·m^-1·K^-1
Expansion coefficient	5.1·10^-6 K^-1

Hardnesses

Mohs hardness	7
Brinell hardness	3,920 NM·m^-2

Elastic properties

Shear modulus	222 GPa
Poisson’s ratio	0.25

Electrical properties

Electrical conductivity	1.09·10⁷ S·m^-1
Resistance	8.1·10^-8 Ωm

Magnetism

Magnetism	paramagnetic
Magnetic susceptibility	1.1·10^-5 cm³·mol⁻¹

Chemical properties

Basicity	slightly acidic
Oxidation state	-2, 0, 2, 3, 4, 6, 8
Standard potential	0.85 V (OsO₄ + 8H⁺ + 8e^- → Os + 4H₂O)

Electronegativity

Pauling scale	2.2
Allred-Rochow scale	1.52
Nagle scale	1.39
Pearson absolute negativity	4.9 eV

Other properties

Natural occurrence	primordial
Crystal structure	Hexagonal close-packed
Goldschmidt Classification	siderophile
Superconductor	with transition tempperature (solid body, normal pressure)
Price/kg	12,000 USD