Tellurium (Te): Atomic Structure and Chemical Properties

Atomic Model Details

Tellurium (Te) is a chemical element with atomic number 52.

• Atomic Symbol: Te
• Atomic Number (Z): 52 (Number of protons)
• Number of Protons: 52
• Number of Electrons: 52 (in a neutral atom)
• Number of Neutrons: Varies with isotope. For the most abundant isotopes:
  • Tellurium-128 (¹²⁸Te): 128 - 52 = 76 neutrons
  • Tellurium-130 (¹³⁰Te): 130 - 52 = 78 neutrons
  • The average atomic mass is 127.60 u.
• Atomic Size:
  • Covalent Radius: Approximately 135 pm
  • Van der Waals Radius: Approximately 206 pm

Electronic Configuration & Shell Diagram

• Electronic Configuration: The ground state electronic configuration of Tellurium is [Kr] 4d¹⁰ 5s² 5p⁴.
• Shell Diagram Representation:
  • K-shell (n=1): 2 electrons
  • L-shell (n=2): 8 electrons
  • M-shell (n=3): 18 electrons
  • N-shell (n=4): 18 electrons
  • O-shell (n=5): 6 electrons (2 in 5s, 4 in 5p – these are valence electrons) Tellurium has 6 valence electrons, which are located in its outermost ‘O’ shell (n=5).

Periodic Trends

Tellurium is a member of Group 16 (Chalcogens) and Period 5 of the periodic table.

• Ionization Enthalpy (1st): The energy required to remove the first electron from a gaseous atom.
  • Value: Approximately 869.3 kJ/mol
  • Trend: Decreases down Group 16 (Oxygen > Sulfur > Selenium > Tellurium).
• Electronegativity (Pauling Scale): A measure of an atom’s ability to attract shared electrons in a chemical bond.
  • Value: Approximately 2.1
  • Trend: Decreases down Group 16. Tellurium is less electronegative than Oxygen, Sulfur, and Selenium.
• Electron Gain Enthalpy: The energy change when an electron is added to a neutral gaseous atom.
  • Value: Approximately -190 kJ/mol (for Te → Te⁻)
  • Trend: Generally becomes less negative (less exothermic) down Group 16 due to increasing atomic size and diffuse electron clouds, making electron addition less favorable.
• Atomic Radius: The average distance from the nucleus to the boundary of the surrounding cloud of electrons.
  • Value (Covalent Radius): Approximately 135 pm
  • Trend: Increases down Group 16 due to the addition of new electron shells.

Key Physical Properties

• Density: 6.24 g/cm³ (at 25°C)
• State at Room Temperature: Solid
• Color: Silvery-white
• Appearance: Brittle, lustrous metalloid. Can be found in crystalline and amorphous forms.
• Melting Point: 449.5 °C
• Boiling Point: 988 °C
• Electrical Conductivity: A semiconductor; its conductivity increases with temperature and exposure to light.
• Nature: Considered a metalloid, exhibiting properties intermediate between metals and nonmetals.