Final answer:
N₂²+ is diamagnetic because in its molecular orbital configuration, all electrons are paired, leading to no magnetic attraction. O₂⁴+, despite having the same number of valence electrons, is paramagnetic due to having two unpaired electrons in its antibonding π* orbitals.
Step-by-step explanation:
The question asks to explain why N₂²+ is diamagnetic, while O₂⁴+, which has the same number of valence electrons, is paramagnetic. The key difference lies in the molecular orbital (MO) configurations and the presence of unpaired electrons.
In the molecular orbital diagram of N₂²+, all the electrons are paired, which results in a diamagnetic molecule.
However, with O₂⁴+, there are two unpaired electrons in the antibonding π* orbitals, even after it loses four electrons. These unpaired electrons cause O₂⁴+ to be paramagnetic and show attraction to a magnetic field.
The concept of paramagnetism and diamagnetism is not determined by the difference in bond order, electronegativity, or molecular weight, but strictly by the presence of unpaired electrons within the molecule's electronic configuration.
Therefore, the presence of unpaired electrons is the correct explanation for the magnetic properties of N₂²+ and O₂⁴+.