An electron that enters bonding orbitals stabilizes the molecule as it’ in between two nuclei. Whereas when an electron is entered into the anti-bonding orbital, it needs to pull an electron away from the nucleus.

When a molecule consists both bonding molecular orbitals and anti-bonding molecular orbitals, the higher the number of bonding orbitals, the more the bonding influence and the more stable the molecule will be and vice-versa.

The formula of bond order is given by ¹⁄₂(N_B – N_A) When N_B is bonding orbitals and N_A is the number of anti-bonding orbitals. In Oxygen, bond order = 1/2(10-6) = 2. When it’s zero the molecule cannot be formed.

The bond length has defined the distance between two atoms in a molecule. The bond order depends on the bond length between two atoms in a molecule. As the bond length increases the bond decreases and vice-versa.

Paramagnetic molecules are attracted by the magnetic field and orbitals are singly occupied. O₂ is an example. Whereas diamagnetic molecules are repelled by the magnetic field, so the option is wrong.