correct order of  electron gain enthalpy is

Electron gain enthalpy ( )Higher Electron gain enthalpy means greater energy is released when electron is added to gaseous isolated atomconsider only magnitude but not the signElectron gain enthalpy of Oxygen is abnormally low  due to the repulsions between added electrons and lonepairs present on it energy released is very lowexpected trend -  O > S > Se > Te > PoActual trend -  S (-200KJ/mole) > Se > Te > Po > O (-141KJ/mole)