Question

First ionization enthalpy of $Mg$ is greater than that of $Ca$ because:

• A. $Z_{eff}$ of $Mg$ is greater than that of $Ca$
• B. Valence electron of $Ca$ is more shielded than that of $Mg$
• C. $Z_{eff}$ of $Ca$ is greater than that of $Mg$
• D. Valence electron of $Ca$ face less force of attraction than that of $Mg$

Answer 1

Answer: (B), (D)

The correct options are
B Valence electron of $Ca$ is more shielded than that of $Mg$
D Valence electron of $Ca$ face less force of attraction than that of $Mg$

$Mg$ ,Atomic Number= 12 ( 2,8,2)
$Ca$ ,Atomic Number= 20 (2,8,8,2)
The valence electrons of calcium are found in the $N$th shell and they are being shielded by the $K,LandM$ shells. whereas the valence electrons in magnesium are found in the $M$th shell and are being shielded by only $K$ and $L$ shells and hence experience greater attraction to the nucleus and hence require more energy to remove.