Tellurium (Te)

Tellurium is a metalloid with atomic number 52, in period 5 and group 16 of the periodic table. Its atomic mass is 127.6 u and its electron configuration is [Kr] 4d¹⁰ 5s² 5p⁴. Solid at 25 °C.

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Key facts

Atomic number	52
Atomic mass	127.6 u
Category	Metalloid
Period	5
Group	16
Block	p
Electron configuration	[Kr] 4d¹⁰ 5s² 5p⁴
Electrons per shell	2, 8, 18, 18, 6
Electronegativity (Pauling)	2.1
Oxidation states	−2, −1, +1, +2, +3, +4, +5, +6common in bold
State at 25 °C	Solid
Melting point	722.66 K449.51 °C
Boiling point	1261 K987.85 °C
Density	6.24 g/cm³

Atomic properties

First ionization energy	9.01 eV
Electron affinity	190.2 kJ/mol
Atomic radius	160 pm
Covalent radius	138 pm
Van der Waals radius	206 pm
Common ions	Te²⁻
Protons, neutrons, electrons	52, 76, 52

Physical and thermal properties

Molar volume	20.46 cm³/mol
Heat of fusion	17.5 kJ/mol
Heat of vaporization	48 kJ/mol
Specific heat	201 J/(kg·K)
Thermal conductivity	3 W/(m·K)
Thermal expansion	1.9 × 10⁻⁵ K⁻¹
Mohs hardness	2.25
Young’s modulus	43 GPa
Crystal structure	Simple trigonal
Magnetic type	Diamagnetic

Identification and history

CAS number	13494-80-9
Latin name	Tellurium
Discovered by	F. Müller von Reichenstein · 1782
Named by	---

Natural isotopes

Isotope	Mass (u)	Abundance
¹²⁰Te	119.904066	0.09 %
¹²²Te	121.903045	2.55 %
¹²³Te	122.904271	0.89 %
¹²⁴Te	123.902818	4.74 %
¹²⁵Te	124.904431	7.07 %
¹²⁶Te	125.903312	18.84 %
¹²⁸Te	127.904461	31.74 %
¹³⁰Te	129.906223	34.08 %

Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.

A dash (---) means there is no reliable published measurement. The app never makes one up.

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