Final answer:
The second ionization energy of magnesium is represented by the equation Mg+ → Mg2+ + e-. This energy is greater because it involves removing an electron from a positively charged ion, which requires overcoming a higher electrostatic attraction according to Coulomb's law.
Step-by-step explanation:
The equation that represents the second ionization energy of magnesium (Mg) is:
- Mg → Mg+ + e-
- Mg+ → Mg2+ + e-
- Mg2+ → Mg3+ + e-
- Mg3+ → Mg4+ + e-
Therefore, the correct equation is the second one, where the Mg+ ion loses an electron to become Mg2+. The second ionization energy is greater than the first because an electron is being removed from an already positively charged ion, which, according to Coulomb's law, requires more energy. As we move further into the ionization process, each successive electron removed from an atom that has a progressively larger positive charge will require even more energy.
In the case of magnesium, the first two electrons are removed from the 3s subshell, while the third ionization energy is much larger, because the third electron is removed from the more tightly bound 2p subshell. This is indicative of the electron configuration and energy levels in atoms which show that electrons are organized in groups within atoms.