![]() ![]() Positive value of bond order indicates that H 2 molecule is stable.īond order value of 1 means that two hydrogen atoms are connected by a single bond. ![]() The electronic configuration of H 2 is ( σ(1s) ) 2 ![]() The electronic configuration of H 2 + is ( σ(1s) ) 1Ģ) Positive bond order means it is stable.ģ) One unpaired electron is present. Greater the number of unpaired electrons present in the molecular or ion, greater is its paramagnetic nature.Įlectronic configuration of Homonuclear Diatomic Molecules If the molecules has some unpaired electrons ,it is paramagnetic in nature. If all the electrons in the molecule are paired, it is diamagnetic in nature. Greater the bond order, shorter is the bond length.Ħ) Diamagnetic and paramagnetic nature of the molecules the bond order is negative or zero.ģ) Relative stability of molecule in terms of bond orderįor diatomic molecules ,the stability is directly proportional to the bond order.Ī molecule with the bond order of 3 is more stable than a molecule with bond order of 2 and so on.Ĥ) Nature of bond in terms of bond order :īond order 1 ,2 and 3 mean single ,double and triple bond.īond length is found to be inversely proportional to the bond order. The molecule is unstable if N b < Na i.e. Σ(1s) Na ,the molecule is stable because greater number of bonding orbitals are occupied than antibonding orbital, resulting in a net force of attraction.Ģ) If N b Na ie. The first ten molecular orbitals may be arranged in order of energy as follow: In MO theory, a star (*) sign always indicates an anti-bonding orbital.įollowing the aufbau ('building up') principle, we place the two electrons in the H 2 molecule in the lowest energy molecular orbital, which is the (bonding) sigma orbital.Energy level diagram for Molecular orbitals The second, sigma-star ( σ *) orbital is higher in energy than the two atomic 1 s orbitals, and is referred to as an anti-bonding molecular orbital. According to MO theory, the first sigma orbital is lower in energy than either of the two isolated atomic 1 s orbitals – thus this sigma orbital is referred to as a bonding molecular orbital. When two atomic 1 s orbitals combine in the formation of H 2, the result is two molecular orbitals called sigma ( σ) orbitals. ![]() The bonding in H 2, then, is due to the formation of a new molecular orbital (MO), in which a pair of electrons is delocalized around two hydrogen nuclei.Īn important principle of quantum mechanical theory is that when orbitals combine, the number of orbitals before the combination takes place must equal the number of new orbitals that result – orbitals don’t just disappear! We saw this previously when we discussed hybrid orbitals: one s and three p orbitals make four sp 3 hybrids. These two new orbitals, instead of describing the likely location of an electron around a single nucleus, describe the location of an electron pair around two or more nuclei. In molecular orbital theory, we make a further statement: we say that the two atomic 1 s orbitals don’t just overlap, they actually combine to form two completely new orbitals. When we described the hydrogen molecule using valence bond theory, we said that the two 1 s orbitals from each atom overlap, allowing the two electrons to be shared and thus forming a covalent bond. Let’s consider again the simplest possible covalent bond: the one in molecular hydrogen (H 2). \)Īnother look at the H 2 molecule: bonding and anti-bonding sigma molecular orbitals ![]()
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