Tellurium
Tellurium is a brittle metalloid that forms useful semiconducting compounds.
Tellurium gives useful electronic behaviour to compounds and alloys.
Explore Tellurium's atom- Atomic number
- 52
- Standard atomic weight
- 127.60(3)
- Family
- Metalloid
- Period
- 5
- Group
- 16
- Standard state
- Solid
In everyday life
Cadmium telluride is used in some thin-film solar cells.
Something to remember
Its name comes from the Latin word for Earth.
Meet its electrons
[Kr] 5s2 4d10 5p4
Published neutral-atom ground-state configuration; excited atoms and ions can differ.
Electrons per shell: 2 · 8 · 18 · 18 · 6.
The playground shows an illustrative shell model. Real electrons are described by quantum orbitals, rather than tiny planets traveling along fixed paths.
A connection to explore
Tellurium and cadmium form a semiconductor compound used in some thin-film solar cells.
Meet Cadmium (Cd)Properties and conditions
- Standard atomic weight
- 127.60(3)CIAAW 2024 standard atomic weight (dimensionless). Parentheses give uncertainty in the last quoted digits. Source flags: g.CIAAW standard atomic weights ↗ · Retrieved 2026-10-15
- Standard state
- SolidPubChem classification, including explicit predictions where stated. Reference temperature and pressure are not supplied in the table.PubChem periodic table ↗ · Retrieved 2026-10-15
- First ionisation energy
- 9.010 eVEnergy to remove the first electron from an isolated neutral gas-phase atom. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electronegativity
- 2.1 Pauling scaleA dimensionless relative measure; values depend on the chosen scale. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Melting point
- 722.66 KPubChem reported value. Pressure, allotrope and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Boiling point
- 1261 KPubChem reported value. Pressure and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Density
- 6.232 g/cm³PubChem reported value. Temperature, pressure, allotrope and measurement uncertainty are not specified in the table; gas densities are especially condition-dependent.PubChem periodic table ↗ · Retrieved 2026-10-15
- Oxidation states
- +6, +4, -2Selected PubChem oxidation states; formal electron bookkeeping, not a list of stable free-ion charges or every possible compound.PubChem periodic table ↗ · Retrieved 2026-10-15
- Discovery
- 1782PubChem discovery attribution. Ancient knowledge and competing priority claims cannot always be represented by a single year.PubChem periodic table ↗ · Retrieved 2026-10-15
- Atomic radius
- 206 pmPubChem tabulated radius. Radius definitions depend on bonding and convention; measurement definition and uncertainty are not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electron affinity
- 1.971 eVPubChem reported gas-phase electron affinity. Sign conventions and electronic states matter; uncertainty is not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
Isotopes, abundance and decay
Isotopes share a proton count but have different neutron counts. This selection includes naturally tabulated compositions and a reference isotope for other elements. It is not a list of every known isotope.
Explore 8 isotopes of Te
| Isotope | Relative atomic mass | Natural fraction | Half-life | Decay |
|---|---|---|---|---|
| Te-120 | 119.9040593(33) | 0.0009(1) | No decay observed | ;2β+ ? |
| Te-122 | 121.9030435(16) | 0.0255(12) | No decay observed | No decay tabulated |
| Te-123 | 122.9042698(16) | 0.0089(3) | No decay observed | ;EC=100 |
| Te-124 | 123.9028171(16) | 0.0474(14) | No decay observed | No decay tabulated |
| Te-125 | 124.9044299(16) | 0.0707(15) | No decay observed | No decay tabulated |
| Te-126 | 125.9033109(16) | 0.1884(25) | No decay observed | No decay tabulated |
| Te-128 | 127.90446128(93) | 0.3174(8) | 2.25 Yy (uncertainty 0.09) | ;2β−=100 |
| Te-130 | 129.906222748(12) | 0.3408(62) | 791 Ey (uncertainty 21) | ;2β−=100 |
Fractions use NIST’s terrestrial isotopic compositions, which can vary by sample. Parentheses denote uncertainty in the last digits. Half-lives and decay branches use NUBASE2020; # marks estimates, >/< mark limits. “No decay observed” follows that evaluation and does not prove permanent stability. Decay branch intensities are percentages; SF means spontaneous fission, EC electron capture, IT an isomeric transition.
Follow the science
Use these original references to explore the data and context. Atomic weights can vary with isotope composition; values for elements without stable isotopes may describe a representative isotope rather than a standard atomic weight.