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

The energy expected to eliminate at least one electron from a neutral atom to generate a positively charged ion is an actual property that impacts the chemical properties of an atom. By definition, the first ionization energy of an element is the energy expected to eliminate the outermost, or most highest energy, electron from an neutral atom in the gas stage.

Complete answer:
$Mg$, Atomic Number $=12\left( 2,8,2 \right)$
$Ca$, Atomic Number $=20\left( 2,8,8,2 \right)$
The valence electrons of calcium are found in the N shell and they are being shielded by the K, L, M shells. Though the valence electrons in magnesium are found in the M shell and are being shielded by just K and L shells and subsequently experience more noteworthy appreciation for the nucleus and thus require more energy to eliminate.
We should initially discover the energy estimation value of the ion we are searching for to locate the main ionization enthalpy. At that point deduct the energy estimation of the neutral atom. This distinction is the ionization energy for that ion.

**Hence, the correct option is B.

Note:**
In general, the first ionization energy increments as we go from left to right directly over a line of the periodic table. The first ionization energy diminishes as we go down a section of the periodic table.