MCQ
The correct sequence of elements in decreasing order of first ionisation energy is
  • A
    $Na > Mg > Al$
  • B
    $Mg > Na > Al$
  • C
    $Al > Mg > Na$
  • $Mg > Al > Na$

Answer

Correct option: D.
$Mg > Al > Na$
d
(d) $Mg > Al > Na$. This is due to the presence of fully filled $s-$orbital in $Mg.$

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