Final answer:
Oxygen (O₂) is the period 2 homonuclear diatomic molecule predicted to be paramagnetic because its MO diagram features two unpaired electrons in the antibonding π* orbitals, unlike N₂, F₂, and Ne₂, which are all diamagnetic. Option B is the correct answer.
Step-by-step explanation:
Paramagnetism arises from the presence of unpaired electrons in an atom or molecule. When electrons are unpaired, they generate magnetic fields that cause the atom or molecule to be attracted to an external magnetic field. For homonuclear diatomic molecules, we can use molecular orbital (MO) theory to predict whether a molecule will be paramagnetic or diamagnetic.
Among the period 2 homonuclear diatomic molecules - Li2, Be2, B2, C2, N2, O2, F2, and Ne2 - oxygen (O2) is known to be paramagnetic due to its electronic configuration. The MO diagram for O2 shows that there are two unpaired electrons in the antibonding π* orbitals (π2py*, π2pz*), which is the signature of a paramagnetic substance.
Nitrogen (N2) has a completely filled MO diagram with no unpaired electrons, making it diamagnetic. Fluorine (F2) and Neon (Ne2) also do not have any unpaired electrons in their MO diagrams and are therefore also diamagnetic. So, the correct option for the homonuclear diatomic molecule predicted to be paramagnetic in period 2 is B. O2 (Oxygen).