Question

Which of the following relations is correct wrt first $\left(I_1\right)$ and second $\left(I_2\right)$ ionization potentials of $Na$ and $Mg$ ?

• A. $I_{1\left(Na\right)}>I_{1\left(Mg\right)}$
• B. $I_{1\left(Mg\right)}=I_{2\left(Na\right)}$
• C. $I_{2\left(Mg\right)}>I_{2\left(Na\right)}$
• D. $I_{2\left(Na\right)}>I_{2\left(Mg\right)}$

Answer 1

The correct option is D $I_{2\left(Na\right)}>I_{2\left(Mg\right)}$

Ionisation Potential is the energy required to pull out an electron from a given atom.
$Na$ has one electron in the outermost shell, it's first ionization energy would be the energy required to pull out this electron. Its second ionization energy would be the energy required to pull out the second electron from a complete shell.
$Mg$ has two electrons in the outermost shell. Its first and second ionization energy would be the energy required to pull out these electrons.
Since we are pulling out the 2nd electron in $Na$ from a very stabilized $N{a}^{+}$, we will require a lot of energy. On the other hand, $Mg$ will give up two electrons very easily. So $Mg$'s $I_2$ would be very less as compared to $I_2$ of $Na$.