Molecular Orbital MO Theory is a method for understanding the electronic structure and bonding in diatomic molecules by considering the combination of atomic orbitals to form molecular orbitals. Molecular orbitals are the allowed energy states for electrons in a molecule, and they can be bonding, non-bonding, or anti-bonding in nature.In the case of H2 hydrogen molecule , each hydrogen atom has one electron in its 1s atomic orbital. According to MO theory, when two hydrogen atoms approach each other, their atomic orbitals overlap and combine to form two molecular orbitals: one bonding 1s and one anti-bonding 1s* . The bonding molecular orbital, 1s, is lower in energy than the original atomic orbitals, while the anti-bonding molecular orbital, 1s*, is higher in energy. The two electrons from the hydrogen atoms will occupy the lower energy bonding orbital 1s , resulting in a stable covalent bond between the two hydrogen atoms. The bond order, which indicates the number of chemical bonds between a pair of atoms, can be calculated as number of electrons in bonding orbitals - number of electrons in anti-bonding orbitals /2. In the case of H2, the bond order is 2-0 /2 = 1, indicating a single bond between the two hydrogen atoms.In the case of N2 nitrogen molecule , each nitrogen atom has five valence electrons: two in the 2s orbital and three in the 2p orbitals. When two nitrogen atoms approach each other, their atomic orbitals combine to form molecular orbitals. The 2s orbitals combine to form a bonding 2s and an anti-bonding 2s* molecular orbital, while the 2p orbitals combine to form three bonding one 2p and two 2p and three anti-bonding one 2p* and two 2p* molecular orbitals.The ten valence electrons from the two nitrogen atoms will fill the molecular orbitals in the order of increasing energy: 2s, 2s*, 2p, 2p, 2p, 2p*, 2p*, and 2p*. The first eight electrons will fill the 2s, 2s*, 2p, and 2p orbitals, leaving two electrons in the 2p orbitals. The bond order for N2 can be calculated as number of electrons in bonding orbitals - number of electrons in anti-bonding orbitals /2 = 8-2 /2 = 3, indicating a triple bond between the two nitrogen atoms.In summary, the molecular orbital theory explains the electronic structure and bonding in diatomic molecules like H2 and N2 by considering the combination of atomic orbitals to form molecular orbitals. The distribution of electrons in these molecular orbitals determines the bond order and the nature of the bond between the atoms in the molecule.