Tellurium (Te)
Element 52 · Metalloid · atomic mass 127.6 u · group 16, period 5
Electron shells: 2, 8, 18, 18, 6
Tellurium is rarer in the crust than platinum and has a habit of announcing itself: exposure gives you garlic breath for weeks. Thin-film solar has become its largest market.
Handle tellurium and you will reek of garlic for days — your body methylates it and you exhale the result.
- Atomic number
- 52
- Atomic mass
- 127.6 u
- Electron configuration
- [Kr] 5s² 4d¹⁰ 5p⁴
- Group · period · block
- 16 · 5 · p
- Oxidation states
- −2, +4, +6
- Electronegativity
- 2.1 (Pauling)
- Melting point
- 450 °C
- Boiling point
- 988 °C
- Density
- 6.232 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery-white, brittle metalloid
- Discovered
- Franz-Joseph Müller von Reichenstein, 1782
52 protons, and 52 electrons when neutral
IUPAC standard atomic weight
Chalcogens
What Tellurium is used for
- Cadmium telluride solar panels
- Rewritable optical media
- Machinable steel and copper alloys
- Thermoelectric coolers
Atomic structure of Tellurium
A neutral tellurium atom has 52 protons and 52 electrons. Its most common isotope carries about 76 neutrons, which is where the mass number 128 comes from. Change the neutron count and you have a different isotope of tellurium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 18, 6. In orbital notation that is [Kr] 5s² 4d¹⁰ 5p⁴, leaving 6 valence electrons in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Tellurium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Tellurium sits in the periodic table
Elements on the staircase between metals and non-metals, showing properties of both. Their intermediate conductivity is what makes semiconductors possible.
Discovery and naming
Tellurium was discovered by Franz-Joseph Müller von Reichenstein in 1782. Its name comes from Latin tellus, "earth".
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Tellurium?
The standard atomic weight of Tellurium is 127.6 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Tellurium have?
Tellurium has 52 protons, because the atomic number is the proton count and that is what makes an atom Tellurium at all. A neutral Tellurium atom has the same number of electrons, 52. The neutron count varies by isotope; the most common one has about 76, since 128 − 52 = 76.
What is the electron configuration of Tellurium?
The electron configuration of Tellurium is [Kr] 5s² 4d¹⁰ 5p⁴. Its electrons are arranged 2, 8, 18, 18, 6 across 5 shells.
Is Tellurium a metal?
Not quite. Tellurium is a metalloid — it sits on the staircase dividing metals from non-metals and shows properties of both, which is exactly why metalloids matter to the semiconductor industry.
What group and period is Tellurium in?
Tellurium is in group 16 (the chalcogens), period 5, in the p-block. The group is its column and the period is its row.
What is the charge of Tellurium?
Tellurium most commonly forms a 2− ion. It is 2 electrons short of a full outer shell, so it gains them rather than losing 6. Across all its compounds it shows oxidation states of −2, +4, +6.
What is the melting point of Tellurium?
Tellurium melts at 450 °C and boils at 988 °C. That puts it in the solids at everyday temperatures.
What is Tellurium used for?
Cadmium telluride solar panels, Rewritable optical media, Machinable steel and copper alloys, Thermoelectric coolers. Tellurium is rarer in the crust than platinum and has a habit of announcing itself: exposure gives you garlic breath for weeks.
Who discovered Tellurium, and where does its name come from?
Tellurium (Te) was discovered by Franz-Joseph Müller von Reichenstein in 1782. The name comes from Latin tellus, "earth".