73TaTantalum

Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, it is named after Tantalus, a figure in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that is highly corrosion-resistant. It is part of the refractory metals group, which are widely used as components of strong high-melting-point alloys. It is a group 5 element, along with vanadium and niobium, and it always occurs in geologic sources together with the chemically similar niobium, mainly in the mineral groups tantalite, columbite and coltan.

The chemical inertness and very high melting point of tantalum make it valuable for laboratory and industrial equipment such as reaction vessels and vacuum furnaces. It is used in tantalum capacitors for electronic equipment such as computers. It is being investigated for use as a material for high-quality superconducting resonators in quantum processors. Tantalum is considered a technology-critical element by the European Commission.

Atomic properties

Standard atomic weight	180.947 ±2·10^-5
Atomic mass	180.947 u

Atomic radii

Radius (empirical)	146 pm
Radius (calculated)	200 pm
Covalent radius	170 ±8 pm

Atomic shell

Electron configuration	Xe 4f¹⁴ 5d³ 6s²
Ionization energy	(1^st) 7.549571 eV (2^nd) 16.2 eV (3^rd) 32.1 eV (4^th) 35 eV (5^th) 48.272 eV
Shell model	Electrons k-shell:2 l-shell:8 m-shell:18 n-shell:32 o-shell:11 p-shell:2

Physical properties

Phase	solid
Density	16.65 g·cm⁻³ (293.1 K)
Molar volume	1.085·10^-5 m³·mol⁻¹
Speed of sound	3,400 m·s⁻¹ (293.1 K)

Temperatures

Melting point	3,290 K
Boiling point	5,731 K
Liquid range	2,441 K
Transition temperature	4.4 K

Enthalpies

Melting enthalpy	36 kJ·mol^-1
Enthalpy of vaporization	735 kJ·mol^-1
Binding energy	782 kJ·mol^-1

Heat and conductivity

Specific heat capacity	140 J·kg⁻¹·K⁻¹
Thermal conductivity	57 W·m^-1·K^-1
Expansion coefficient	6.3·10^-6 K^-1

Hardnesses

Mohs hardness	6.5
Brinell hardness	800 NM·m^-2
Vickers hardness	873 NM·m^-2

Elastic properties

Young’s modulus	186 GPa
Shear modulus	69 GPa
Bulk modulus	200 GPa
Poisson’s ratio	0.34

Electrical properties

Electrical conductivity	7.61·10⁶ S·m^-1
Resistance	1.35·10^-7 Ωm

Magnetism

Magnetism	paramagnetic
Magnetic susceptibility	1.54·10^-4 cm³·mol⁻¹ (293 K)

Optical properties

Reflectivity	78 %

Chemical properties

Basicity	slightly acidic
Oxidation state	5
Standard potential	-0.81 V (½Ta₂O₅ + 5H⁺ + 5e^- → Ta + 2½H₂O)

Electronegativity

Pauling scale	1.5
Allred-Rochow scale	1.33
Nagle scale	1.26
Pearson absolute negativity	4.11 eV

Other properties

Natural occurrence	primordial
Crystal structure	Body-centered cubic
Goldschmidt Classification	lithophile
Superconductor	with transition tempperature (solid body, normal pressure)
Price/kg	305 ±7 USD