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Explain the variations in the following properties of group-18 elements : (i) Atomic radii (ii) Ionisation enthalpy (iii) Electron gain enthalpy |
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Answer» Solution :(i) Atomic radii: The atomic radii of noble gases in their respective periods are exceptionally high because incase of noble gases, the atomic radii corresponds to Van-der-Waal.s radii which is ALWAYS larger than covalent radii. Down the group, the atomic radii increases with the increase in atomic number. (ii) Ionisation enthalpy : Ionisation enthalpies of noble gases are exceptionally high DUE to presence of fully filled valence SHELLS. However down the group the ionisation enthalpy decreases. (iii) ELECTRON gain enthalpy : The values of electron gain enthalpies are LARGE positive as they have fully filled valance shells. Hence, they have no tendency to accept electrons and form anions |
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