Atomic and Ionic Radii Anomalies

Trend Relationships: $$\text{Van der Waals Radius} > \text{Metallic Radius} > \text{Covalent Radius} \qquad

\text{and} \qquad \text{Isoelectronic Radius} \propto \frac{1}{Z}$$

Concept: Non-bonded structural radii always outsize bonding pairs due to dispersion boundary interactions, whereas isoelectronic configurations contract systematically with increasing atomic numbers.

Notation: $$\text{Isoelectronic species order: } \text{O}^{2-} > \text{F}^- > \text{Na}^+ > \text{Mg}^{2+} > \text{Al}^{3+}$$;

• $$Z$$ = Number of Protons.