What do you mean by significane of the terms "isolated gaseous atoms " and ground state while defining ionisation enthalpy and electron gain enthalpy

Isolated means set or kept apart from others and we detached an atom from the set of group of atom( as an elements consist of so many atoms in it ) and study about the ionisation energy and electron gain enthalpy of that atom is termed as "isolated gaseous atom".

 

Ground state is the state of a physical system having the lowest possible potential energy. For example, an electron in the lowest energy orbital in a hydrogen atom is in a ground state. The ground state of a physical system tends to be stable unless energy is applied to it from the outside; states that are not the ground state have a tendency to revert to the ground state, giving off energy in the process. Compare excited state.