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JEE MainChemistryClassification of Elements and Periodicity in Properties

The correct increasing order of the first ionization enthalpies of Mg , Al , P and S is

Options

  1. AMg < Al < P < S
  2. BP < S < Al < Mg
  3. CAl < Mg < P < S
  4. DAl < Mg < S < P

Correct answer

D. Al < Mg < S < P

Step-by-step solution

The general trend is an increase in first ionization enthalpy across a period from left to right. However, there are exceptions due to stable electronic configurations. Magnesium ( Mg ) has a completely filled 3s subshell ( [ Ne ] 3s^2 ), making its ionization enthalpy higher than that of Aluminium ( Al , [ Ne ] 3s^2 3p^1 ). Phosphorus ( P ) has a stable half-filled 3p subshell ( [ Ne ] 3s^2 3p^3 ), making its ionization enthalpy higher than that of Sulphur ( S , [ Ne ] 3s^2 3p^4 ). Therefore, the correct increasin

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