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Te

Tellurium

Tellurium (Te) is a metalloid with atomic number 52 and an atomic mass of 127.6. Its electron configuration is [Kr] 4d10 5s2 5p4, which gives it 6 valence electrons.

Tellurium key data

Symbol Te
Atomic number 52
Atomic mass (standard atomic weight) 127.6
Molar mass 127.6 g/mol
Protons 52
Neutrons (most abundant isotope, tellurium-130) 78
Electrons (neutral atom) 52
Valence electrons 6
Category Metalloid
Period 5
Group 16
Block p-block
Noble gas notation [Kr] 4d10 5s2 5p4
Full electron configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p4
Electrons per shell 2, 8, 18, 18, 6

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.

Measured properties of tellurium

From PubChem, the US National Institutes of Health. Public domain.

Melting point 722.66 K (449.51 °C), 70th of 103 by melting point
Boiling point 1261 K (987.85 °C), 68th of 93 by boiling point
Density 6.232 g/cm³, 56th of 96 by density
State at room temperature Solid
Electronegativity 2.1 (Pauling), 26th of 95 by electronegativity
Van der Waals radius 206 pm, joint 55th of 99 by atomic radius
First ionisation energy 9.01 eV (869 kJ/mol), 24th of 102 by first ionisation energy
Electron affinity 1.971 eV (190.2 kJ/mol), 10th of 57 by electron affinity
Common oxidation states +6, +4, −2
Discovered 1782

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Tellurium electron configuration

The full electron configuration of tellurium is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p4. With the noble-gas core collapsed it is [Kr] 4d10 5s2 5p4, and the outermost subshell is 5p4.

Bohr model of tellurium (Te): a nucleus and five shells holding 2, 8, 18, 18 and 6 electrons from the inside out.
Bohr model of tellurium (Te). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.
Orbital box diagram of tellurium (Te), [Kr] 4d10 5s2 5p4, with the krypton core drawn as one bar: one box per orbital, filled by Hund’s rule, showing two unpaired electrons, in 5p.
Orbital diagram of tellurium (Te). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one tellurium atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

  1. one atom = 127.6 / (6.02214076 × 10²³)
  2. = 2.1188 × 10⁻²² g

Atoms in one gram

  1. atoms per gram = 6.02214076 × 10²³ / 127.6
  2. = 4.7195 × 10²¹ atoms

Tellurium on the periodic table

Tellurium is in period 5, group 16, in the p-block.

The other elements of group 16 are oxygen, sulfur, selenium, polonium and livermorium.

The rest of period 5

Work with tellurium