Tellurium
Atomic Data
| Atomic Number | 52 |
| Symbol | Te |
| Atomic Weight | 127.6 u |
| Density (STP) | 6.24 g/cm³ |
| Melting Point | 449.51 °C (722.66 K) |
| Boiling Point | 987.85 °C (1261 K) |
| Electronegativity | 2.1 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p4 |
| Oxidation States | −2, +2, +4, +6 |
| Phase at STP | Solid |
| Category | Metalloid |
| Period / Group | 5 / 16 |
| CAS Number | 13494-80-9 |
Electron Configuration
[Kr] 4d10 5s2 5p4
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| O | 5 | 5s | 2 | 48 |
| O | 5 | 5p | 4 | 52 |
| Total | 52 | 52 | ||
Isotopes of Tellurium
Tellurium has eight naturally occurring stable isotopes. The most abundant is ¹³⁰Te, comprising 34.08% of all naturally occurring Tellurium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Tellurium-120 | ¹²⁰Te | 52 | 68 | 0.09 | Stable |
| Tellurium-122 | ¹²²Te | 52 | 70 | 2.55 | Stable |
| Tellurium-123 | ¹²³Te | 52 | 71 | 0.89 | Stable |
| Tellurium-124 | ¹²⁴Te | 52 | 72 | 4.74 | Stable |
| Tellurium-125 | ¹²⁵Te | 52 | 73 | 7.07 | Stable |
| Tellurium-126 | ¹²⁶Te | 52 | 74 | 18.84 | Stable |
| Tellurium-128 | ¹²⁸Te | 52 | 76 | 31.74 | Stable |
| Tellurium-130 | ¹³⁰Te | 52 | 78 | 34.08 | Stable |
Abundance & Occurrence
Tellurium is present in Earth's crust at approximately 0.001 ppm by mass and at approximately 9 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Tellurium vapour and compounds: systemic toxicity: Even trace exposures to tellurium or its compounds cause a characteristic persistent garlic odour on the breath and in perspiration (dimethyl telluride excretion); higher exposures cause nausea, somnolence, and potentially serious systemic toxicity.
- Hydrogen telluride (H2Te): H2Te is a toxic gas more dangerous than hydrogen sulfide; even brief exposure causes respiratory irritation, eye damage, and systemic poisoning: handle only in ventilated systems.
- Tellurium dioxide dust: TeO2 dust is moderately irritating to respiratory tract; avoid inhaling any tellurium compound dusts or fumes.
- General handling: Wear nitrile gloves, eye protection, and a respiratory mask when handling tellurium or its compounds; any spills on skin will result in characteristic odour persisting for days despite washing.
Tellurium in the Real World
Real-World Uses
- CdTe photovoltaic solar cells: Tellurium is an essential element in cadmium telluride (CdTe) thin-film solar cells, which are the most commercially successful thin-film photovoltaic technology, with gigawatts of capacity installed worldwide.
- Thermoelectric devices: Bismuth telluride (Bi₂Te₃) and lead telluride (PbTe) thermoelectrics convert waste heat to electricity and provide solid-state cooling in Peltier modules used in electronics thermal management and portable refrigerators.
- Steel and copper alloy additive: Small tellurium additions improve the machinability of steel and copper alloys by forming fine telluride inclusions that promote chip breaking during machining, reducing tool wear.
- Phase-change data storage: Tellurium alloys (GeTeSb) undergo rapid reversible amorphous-crystalline phase transitions; this property was exploited in rewritable CD-RW, DVD-RW, and phase-change memory (PCM) storage devices.
- Semiconductor precursors: Diethyl telluride and dimethyl telluride are precursors for depositing telluride compound semiconductor films by MOCVD in the manufacture of II-VI semiconductor devices.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is tellurium used for?
Tellurium is used mainly in metallurgy: small additions to steel and copper improve machinability, and tellurium is added to lead to improve its strength and corrosion resistance. Cadmium telluride (CdTe) is an important thin-film solar cell material used by companies such as First Solar. Bismuth telluride is the leading thermoelectric material for small-scale cooling devices (Peltier coolers).
Is tellurium rare?
Tellurium is one of the least abundant elements in Earth's crust, with an abundance of about 1 part per billion: rarer than platinum. Most tellurium is recovered as a byproduct of copper refining, from the anode slime left during electrolytic copper purification. Its rarity and the growth of CdTe solar cells have raised supply security concerns.
How was tellurium discovered?
Tellurium was discovered in 1782 by Hungarian mineralogist Franz-Joseph Müller von Reichenstein in a gold ore from Transylvania. He suspected it was a new element but was uncertain. Martin Heinrich Klaproth confirmed it as a new element in 1798 and named it after Tellus, the Roman goddess of Earth, maintaining the celestial naming theme established by uranium (Uranus) and selenium (Moon/Selene).
What does tellurium smell like?
Tellurium is famous among chemists for its extremely unpleasant smell. Even tiny quantities of tellurium absorbed through the skin or inhaled are metabolised in the body to dimethyl telluride, which causes a persistent, intensely garlic-like odour from the breath and sweat that can last for weeks. This makes tellurium handling in the lab a memorable and unwelcome experience.