BohriumElectron Configuration, Bohr Model, Valence Electrons & Orbital Diagram

The electron configuration of Bohrium is written as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f¹⁴ 6d⁵ 7s². Applying the Aufbau principle — filling orbitals from lowest to highest energy — plus the Pauli Exclusion Principle and Hund's Rule, we systematically place all 107 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f¹⁴ 6d⁵ 7s². Transition metals like Bohrium are defined by d-orbital filling. The five d-orbitals can hold up to 10 electrons and are responsible for Bohrium's characteristic bonding behavior, colored compounds, and catalytic activity.

Bohrium follows the standard Aufbau filling order without exception. The noble gas shorthand [Rn] 5f¹⁴ 6d⁵ 7s² replaces the inner-shell electrons with the symbol of the preceding noble gas, highlighting that only the outer electrons — 5f¹⁴ 6d⁵ 7s² — 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, Bohrium's 107 electrons are distributed as: K-shell (n=1): 2 electrons; L-shell (n=2): 8 electrons; M-shell (n=3): 18 electrons; N-shell (n=4): 32 electrons; O-shell (n=5): 32 electrons; P-shell (n=6): 13 electrons; Q-shell (n=7): 2 electrons. The Q-shell (n=7) is the valence shell, containing 7 electrons.

Chemically, this configuration places Bohrium in Group 7 with oxidation states of 7. The partially (or fully) filled d-subshell is the source of Bohrium's variable valency, colored compounds, and catalytic behavior.

The SPDF orbital model describes Bohrium'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. Bohrium's 107 electrons occupy 18 distinct subshells: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f¹⁴ 6d⁵ 7s², governed by three quantum mechanical rules.

The Pauli Exclusion Principle ensures no two electrons in Bohrium 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 107 electrons would collapse into the 1s orbital. For Bohrium's d-electrons, Hund's Rule requires filling each of the five d-orbitals singly before pairing. This maximizes electron spin, producing Bohrium's characteristic magnetic moment and explaining its tendency toward specific oxidation states.

Following standard orbital filling, Bohrium 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 7s² subshell, making Bohrium a d-block element with 7 valence electrons in Group 7.

The outermost electrons — 7s² — are Bohrium's chemical agents. Understanding the 7s² occupancy — how many electrons, whether paired or unpaired, the orbital shape involved — is the foundation for predicting Bohrium's bonding geometry, oxidation behavior, and compound formation.

Bohrium's chemical reactivity is shaped by three interlocking properties: electronegativity, first ionization energy, and electron affinity (0 eV). Its electronegativity is not measurable (noble gas — no electronegativity scale applies).

Bohrium's ionization energy pattern reflects its block and period positioning, consistent with the expected periodic trend for Transition Metal elements.

Bohrium's reactivity varies by oxidation state and chemical environment. Its d-electrons enable multiple oxidation states (7), making it valuable in both redox and coordination chemistry.

Placing Bohrium between Seaborgium (Z=106) and Hassium (Z=108) reveals the incremental property changes that make the periodic table a predictive tool.

Seaborgium → Bohrium: adding one proton and one electron increases nuclear charge by 1. Valence electrons shift from 6 to 7 (Group 6 → Group 7). . Atomic radius decreases from 143 pm to 141 pm, consistent with increasing nuclear pull across a period.

Bohrium → Hassium: the additional proton and electron in Hassium changes the valence electron count from 7 to 8, crossing from Group 7 to Group 8. Both elements share Transition Metal character, with Hassium exhibiting slightly different electronegativity. These comparisons confirm that Bohrium sits at a well-defined chemical inflection point in the periodic table.