Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): B ₂ molecule is paramagnetic, whereas C ₂ molecule is diamagnetic. Reason (R): In B ₂ and C ₂ molecules, the 2p_x and 2p_y molecular orbitals are lower in energy than the 2p_z molecular orbital. In the light of the above statements, choose the most appropriate answer from the options given below:

Step-by-step solution

Assertion is correct: According to Molecular Orbital Theory, the electronic configuration of B ₂ (10 e^- ) is 1s^2 ^ * 1s^2 2s^2 ^ * 2s^2 2p_x^1 = 2p_y^1 . It has two unpaired electrons, making it paramagnetic. The configuration of C ₂ (12 e^- ) is 1s^2 ^ * 1s^2 2s^2 ^ * 2s^2 2p_x^2 = 2p_y^2 . All electrons are paired, making it diamagnetic. Reason is correct: For homonuclear diatomic molecules up to 14 electrons (like B ₂ and C ₂ ), due to s-p mixing, the energy of the 2p_z orbital is raised above the 2p_x and 2p_