Multiple choice

Which of the following order of first ionization energy (IE1) is false?

  1. B > Al > Ga

  2. Li > Na > K

  3. C > Si > Ge

  4. Be > Mg > Ca

  5. C > Be > B
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A Correct answer
Explanation

Unlike expected order of first ionization enthalpies (IE1) i.e., B > Al > Ga, the actual order of IE1 is B > Ga > Al. Because of small atomic size and greater effective nuclear charge, the valence electrons of Ga are held more tightly than Al. Hence, IE1 of Ga is more than that of Al.

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