From Electronegativity towards Reactivity-Searching for a Measure of Atomic Reactivity

Area of Science:

• Quantum Chemistry
• Atomic Physics
• Chemical Bonding Theory

Background:

• Linus Pauling's concept of electronegativity is crucial for understanding bond polarity and ionic character.
• Existing definitions of electronegativity, like Mulliken's and Pauling's, provide a foundation for related atomic properties.

Purpose of the Study:

• To define and quantify atomic reactivity, analogous to electronegativity.
• To develop measures that distinguish nonreactive inert gas atoms from other elements.
• To predict the stability of covalent bonds in molecules using atomic reactivity.

Main Methods:

• Proposed new definitions for atomic reactivity based on ionization energies and bond energies.
• Utilized bond energies in atomic hydrides to establish a useful measure of atomic reactivity.
• Applied concepts of atomic structure, including the Aufbau model and ground state degeneracy, to explain reactivity.
• Estimated atomic strain energy using a simplified Thomas-Fermi density functional theory (DFT) approach.

Main Results:

• Three distinct measures of atomic reactivity were proposed, successfully differentiating inert gases.
• Atomic reactivity was linked to the degeneracy of atomic ground states; reactive atoms exhibit degenerate or near-degenerate states, while inert atoms have non-degenerate states.
• A strong correlation was found between estimated atomic strain energy and atomic reactivity measures.

Conclusions:

• The proposed atomic reactivity measures provide a framework for understanding chemical bonding and molecular stability.
• Atomic reactivity originates from the symmetry of the atomic environment and associated conservation laws, influencing atomic structure and the periodic table.
• Strain energy within atomic electron structures, influenced by symmetry constraints, is a key factor in atomic reactivity, though antibonding effects modulate its impact on bonding.