COMEDK2024ChemistryClassification of Elements and Periodicity in PropertiesActual
Among the following, which is not according to the property indicated against it?
Options
- AI < Br < F < Cl [Increasing Elecrtron Gain Enthalpy with negative sign]
- BB < C < N < O [Increasing First Ionisation Enthalpy]
- CMg ²⁺< Na ⁺< F ⁻< O ²⁻ [Increasing Ionic Size]
- DNa < K < Rb < Cs [Increasing Metallic Radii]
Correct answer
B. B < C < N < O [Increasing First Ionisation Enthalpy]
Step-by-step solution
Option (1): The electron gain enthalpy (magnitude) for halogens follows the order I Option (2): The first ionization enthalpy generally increases across a period. However, N has a stable half-filled 2p^3 configuration, making its ionization enthalpy higher than that of O . The correct order is B Option (3): For isoelectronic species, the ionic size increases as the nuclear charge decreases. The nuclear charges are Mg ²⁺ (12) , Na ⁺ (11) , F ⁻ (9) , and O ²⁻ (8) . The order Mg ²⁺ Option (4): Metallic radii increase