Bohrium (Bh) - Chemical Element Revision Guide

Introduction to Bohrium (Bh)

Bohrium (Bh) is a synthetic chemical element with atomic number 107. It is named after the Danish physicist Niels Bohr.

• Synthetic Element: Bohrium does not occur naturally on Earth. It is exclusively produced in laboratories through nuclear fusion reactions.
• Heavy Element: It is classified as a heavy element due to its high atomic mass (mass number of its isotopes ranges from approximately 261 to 278).
• Rare Element: Only a handful of atoms of Bohrium have ever been synthesized, making it exceedingly rare. Its fleeting existence and minute quantities prevent any practical macroscopic applications.

Periodic Table Placement

Bohrium’s position in the periodic table helps predict its chemical and physical properties.

• Atomic Number (Z): 107
• Group: 7 (VIIB). It is positioned below Manganese (Mn), Technetium (Tc), and Rhenium (Re), and is therefore expected to exhibit properties analogous to these elements, particularly Rhenium.
• Period: 7
• Block: d-block (specifically, a transactinide element, also known as a superheavy element).
• Electronic Configuration (Predicted): [Rn] 5f¹⁴ 6d⁵ 7s²
  • [Rn] represents the electron configuration of Radon, the noble gas preceding Bohrium.
  • The 5f¹⁴ subshell is completely filled.
  • The 6d⁵ and 7s² electrons are the valence electrons, contributing to its chemical behavior as a transition metal.

Radioactivity & Stability

All known isotopes of Bohrium are highly radioactive and unstable.

• Most Stable Isotope: ²⁷⁴Bh
• Half-life: The half-life of ²⁷⁴Bh is approximately 61 seconds. Other isotopes have even shorter half-lives (e.g., ²⁷²Bh has a half-life of ~10 seconds).
• Type of Decay: Bohrium isotopes primarily undergo alpha (α) decay, where an alpha particle (a helium nucleus, ²₄He) is emitted. Spontaneous fission is also observed as a decay mode for some isotopes.

Scientific Importance

Due to its extreme instability and scarcity, Bohrium has no common applications. Its importance lies solely in fundamental scientific research.

• Synthetic Production: Bohrium is synthesized by bombarding heavy target nuclei with lighter ions. A common reaction involves fusing bismuth-209 with chromium-54 ions: ²⁰⁹Bi + ⁵⁴Cr → ²⁶²Bh + 1n (where ‘n’ is a neutron).
• Research into Superheavy Elements: The study of Bohrium contributes to understanding the nuclear structure and properties of superheavy elements. It helps scientists explore the theoretical concept of an “island of stability” – regions of the periodic table where certain superheavy isotopes are predicted to have longer half-lives than their neighbors.
• Validation of Chemical Theories: Although challenging due to its short half-life and single-atom scale experiments, studying the chemical properties of Bohrium helps validate theoretical predictions about how relativistic effects influence the electronic structure and chemical behavior of superheavy elements, particularly its expected resemblance to Rhenium.