In molecules like CO, orbital energies are unequal so bonding orbitals resemble the more electronegative atom.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
In heteronuclear diatomic molecules the two atoms have different electronegativities, so their atomic orbitals differ in energy. The bonding molecular orbitals lie closer in energy to the orbitals of the more electronegative atom and therefore resemble them more closely. Antibonding orbitals resemble the orbitals of the less electronegative atom. Electron density is thus drawn toward the more electronegative atom, which represents bond polarity within MO theory. The orbital ordering can also differ from that of homonuclear molecules because of these energy differences.
Key ideas: Key steps: the more electronegative atom has lower-energy atomic orbitals, so the bonding MO is mostly that atom and the antibonding MO is mostly the other. Use the same count rules as for homonuclear. Examples: CO and CN- and NO+ are isoelectronic with N2 with bond order 3, and NO has 11 electrons, with its odd electron in a pi star orbital (bond order 2.5).
Common mistakes and connections: A typical mistake is placing atomic energy levels at equal height for CO or NO, or using the O2 ordering for CO. Also forgetting that the HOMO of CO is a sigma orbital with lone pair character on carbon, which explains the way CO bonds to metals through carbon. Links to bond polarity, metal carbonyls and radicals.
In CO the oxygen orbitals lie lower than carbon orbitals, so bonding MOs resemble oxygen and antibonding MOs resemble carbon. The interactive lesson shows this as a live animation or chart.
Carbon monoxide is isoelectronic with N2 and has a bond order of 3, but its bonding orbitals are polarized toward oxygen.
In molecules like CO, orbital energies are unequal so bonding orbitals resemble the more electronegative atom.
Heteronuclear Diatomic MOs is a advanced topic in Bonding & Molecular Structure. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Bonding & Molecular Structure first: Paramagnetism of Oxygen, Diamagnetism, Paramagnetism.
The next topics in Bonding & Molecular Structure are Delocalization and Benzene Bonding.
Yes. The interactive lesson includes a self-check question on Heteronuclear Diatomic MOs, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Heteronuclear Diatomic MOs is topic 66 of 104 in Bonding & Molecular Structure.