The (atomic radius, ionization energy, electronegativity) all emerge from quantum mechanics. For instance, ionization energy increases across a period because increasing nuclear charge (Z) pulls electrons closer without additional shielding—quantified by Slater’s rules and effective nuclear charge (Z_eff).
Dmitri Mendeleev’s 1869 table was revolutionary, but it was based on empirical observations. The modern quantum mechanical model explains why elements behave similarly: because of the arrangement of electrons in atomic orbitals defined by four quantum numbers: The (atomic radius
The International Union of Pure and Applied Chemistry provides an official, high-resolution PDF with atomic weights updated. While not explicitly “quantum,” it includes electron configurations. The (atomic radius
Electrons occupy orbitals of the same energy singly before pairing up. 5. Conclusion The (atomic radius