TelluriumElectron Configuration, Bohr Model, Valence Electrons & Orbital Diagram

The electron configuration of Tellurium is written as <strong>1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁴</strong>. Applying the Aufbau principle — filling orbitals from lowest to highest energy — plus the Pauli Exclusion Principle and Hund's Rule, we systematically place all 52 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁴. The p-subshell adds three dumbbell-shaped orbitals (p_x, p_y, p_z) that collectively hold up to 6 electrons. In Tellurium, these outermost p-orbitals are the seat of its chemical personality — more than half-filled, driving electron acceptance.

Tellurium follows the standard Aufbau filling order without exception. The noble gas shorthand <strong>[Kr] 4d¹⁰ 5s² 5p⁴</strong> replaces the inner-shell electrons with the symbol of the preceding noble gas, highlighting that only the outer electrons — 4d¹⁰ 5s² 5p⁴ — are chemically active. Note: for Period 4+ elements, the 4s orbital fills before 3d per Madelung's rule, even though 3d ends at a lower energy in the final atom.

Shell-by-shell, Tellurium's 52 electrons are distributed as: K-shell (n=1): <strong>2</strong> electrons; L-shell (n=2): <strong>8</strong> electrons; M-shell (n=3): <strong>18</strong> electrons; N-shell (n=4): <strong>18</strong> electrons; O-shell (n=5): <strong>6</strong> electrons. The O-shell (n=5) is the valence shell, containing 6 electrons.

Chemically, this configuration places Tellurium in Group 16 with oxidation states of 6, 4, 2, -2. This configuration directly predicts Tellurium's bonding mode, reactivity toward oxidizing and reducing agents, and the stoichiometry of its most common compounds.

The SPDF orbital model describes Tellurium's electrons not as planetary orbits but as three-dimensional probability clouds — each orbital a region of space where an electron is most likely to be found. Tellurium's 52 electrons occupy 11 distinct subshells: <strong>1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁴</strong>, governed by three quantum mechanical rules.

<strong>The Pauli Exclusion Principle</strong> ensures no two electrons in Tellurium share the same four quantum numbers (n, l, m_l, m_s). This is why the 1s orbital holds only 2 electrons, the full p-subshell holds 6, d holds 10, and f holds 14. Without this rule, all 52 electrons would collapse into the 1s orbital. <strong>Hund's Rule of Maximum Multiplicity is critical in Tellurium's p-subshell: the three p-orbitals (p_x, p_y, p_z) must each receive one electron before any pairing occurs. This minimizes electron-electron repulsion and explains Tellurium's 3 paired and 0 empty p-orbitals.</strong>

Following standard orbital filling, Tellurium fills orbitals in the sequence: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p. The final electron enters the <strong>5p⁴</strong> subshell, making Tellurium a p-block element with 6 valence electrons in Group 16.

The outermost electrons — <strong>5p⁴</strong> — are Tellurium's chemical agents. Understanding the 5p⁴ occupancy — how many electrons, whether paired or unpaired, the orbital shape involved — is the foundation for predicting Tellurium's bonding geometry, oxidation behavior, and compound formation.

Tellurium's chemical reactivity is shaped by three interlocking properties: electronegativity (2.1 Pauling), first ionization energy (9.01 eV), and electron affinity (1.971 eV). Its electronegativity is moderate (2.1) — capable of both polar covalent and some ionic bonding. This mid-scale electronegativity enables Tellurium to participate in both polar covalent and ionic bonding depending on its partner.

The first ionization energy of 9.01 eV sits in the moderate range, allowing some ionic character in the right partner combinations. The electron affinity of 1.971 eV represents the energy released when Tellurium gains one electron, indicating a meaningful but moderate acceptance of electrons.

In standard chemical conditions, Tellurium forms diverse compounds across multiple oxidation states, consistent with its 6 valence electrons and p-block character.

Placing Tellurium between Antimony (Z=51) and Iodine (Z=53) reveals the incremental property changes that make the periodic table a predictive tool.

Antimony → Tellurium: adding one proton and one electron increases nuclear charge by 1. Valence electrons shift from 5 to 6 (Group 15 → Group 16). Electronegativity: 2.05 → 2.1 | Ionization energy: 8.608 → 9.01 eV. Atomic radius decreases from 133 pm to 123 pm, consistent with increasing nuclear pull across a period.

Tellurium → Iodine: the additional proton and electron in Iodine changes the valence electron count from 6 to 7, crossing from Group 16 to Group 17. This boundary also marks a categorical transition from Metalloid to Halogen. These comparisons confirm that Tellurium sits at a well-defined chemical inflection point in the periodic table.