Explain why the second ionisation energy of sodium is greater than the second ionisation energy of magnesium.
- AThe attraction between the nucleus and the outer electron is greater in $\text{Na}^+$ than in $\text{Mg}^+$.
- BThe nuclear charge of $\text{Na}^+$ is greater than that of $\text{Mg}^+$.
- CThe outer electron of $\text{Na}^+$ is more shielded than the outer electron of $\text{Mg}^+$.
- DThe outer electron of Na is in the same orbital as the outer electron of Mg.