What is the significance of the terms-'Isolated gaseous atom' and 'ground tate' while defining the ionisation enthalpy ad electron-gain enthalpy?

Explanation

Ionisation energy of an element is defined as the minimum amount of energy required to remove the most loosely bound electron from the valence shell of an isolated gaseous atom existing in its ground state so as to form a cation in the gaseous state.
electron gain enthalpy is defined as the enthalpy change involved when an electron is added to an isolated gaseous atom in its lowest energy state (ground state) to form a gaseous ion carrying unit negative charge.
the force with which an electron gets attracted by the nucleus of an atom is influenced by the presence of other atoms in the molecule or in the neighbourhood. thus, to determine the iohnisation enthalpy. the interatomic forces should be minimum. interatomic forces are minimum to case of gaseous state as the atoms are far apart from each other. consequently, the value of ionisation enthalpy is less affected by the surroundings. similarly, for electron affinity, the interatomic forces of attraction should be minimum for the corresponding atom.for this reason, the term "isolated gaseous atom' is used while defining ionisation enthalpy and electron-gain enthalpy. ground state means the state at which the atom exists. in the most stable state. if the atom is in the excited state, then amount of heat applied to remove an electron or the amount of heat liberated due to addition of an electron is low. so, for the pupose of comparison the term 'ground state' is used while defining ionisation enthalpy and electron-gain enthalpy.