What is the significance of the terms — ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy? Hint: Requirements for comparison purposes.
The term isolated gaseous atom is significant because it ensures that the atom is free from any interatomic interactions or bonding forces present in solid or liquid states. This provides a standard condition to accurately measure the energy required to remove or add an electron, which is essential for comparison purposes among different elements.
The term ground state signifies that the atom is in its lowest energy state before the electron is removed or added. If the atom were in an excited state, the measured energy would vary depending on the level of excitation. Defining the enthalpy changes based on the ground state ensures a consistent and standard baseline for comparing the tendency of elements to lose or gain electrons.
Explanation
Ionization enthalpy and electron gain enthalpy are defined for an isolated gaseous atom in its ground state to provide a standard reference point. Isolation in the gaseous phase removes external interatomic forces, while the ground state condition ensures the electron being removed or added is from the lowest possible energy level, making the values comparable across different elements.