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(a) Define ionization energy. (b) Prove that ionization energy is a periodic property. |
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Answer» Solution :(a) The energy required to remove the most loosely held electron from an isolated gaseous atom is called as ionization energy. (b) Variation in a PERIOD: On moving across a period from left to right, the ionization enthalpy value increases. This is due to the following REASONS: • Increase of NUCLEAR charge in a period • Decrease of atomic size in a period Because of these reasons, the valence ELECTRONS are held more tightly by the nucleus, thus ionization enthalpy increases. Hence, ionization energy is a periodic property. (ii) Variation in a group: As we move from top to bottom along a group, the ionization enthalpy decreases. This is due to the following reasons: • A gradual increase in atomic size • Increase of screening effect on the outermost electrons due to the increase of NUMBER of inner electrons. Hence, ionization enthalpy is a periodic property. |
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