H2+ is the simplest molecule, a one-electron system explained by molecular orbital theory.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
The hydrogen molecule ion, H2+, consists of two protons and a single electron, making it the simplest possible molecule. Because it has only one electron, its wavefunction can be calculated exactly, which provides an ideal test of molecular orbital theory. The electron occupies a bonding molecular orbital spread over both nuclei, lowering the energy compared with a separated proton and hydrogen atom. The ion has a bond energy of about 255 kJ/mol and a bond length of about 106 pm. Its study established the basis for understanding covalent bonds in molecules.
Key ideas: Use it to teach MO theory in its simplest form: linear combination of two 1s orbitals gives sigma 1s with energy below the hydrogen 1s and sigma star 1s above. One electron in the bonding orbital gives bond order 0.5. Compare dissociation energies: H2+ is 255 kJ/mol, H2 is 436 kJ/mol, and bond lengths 106 pm and 74 pm.
Common mistakes and connections: Students believe a covalent bond always needs a pair of electrons, but one electron can hold two nuclei together. Another error is thinking H2+ is unstable and does not exist: it is found in interstellar space and in plasmas. Also, comparing with H2, adding the second electron shortens the bond. Links to MO theory, bond order and ionization.
H2+ has one electron holding two protons together, with a bond energy of 2.65 eV at a bond length of 106 pm, weaker and longer than neutral H2. The interactive lesson shows this as a live animation or chart.
The H2+ ion has a bond energy of about 255 kJ/mol, which is weaker than the bond in neutral H2.
H2+ is the simplest molecule, a one-electron system explained by molecular orbital theory.
Hydrogen Molecule Ion 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: High Spin and Low Spin Complexes, Color of Transition Metal Complexes, Isomerism in Complexes.
The next topics in Bonding & Molecular Structure are Hypervalency and Three-Center Two-Electron Bond.
Yes. The interactive lesson includes a self-check question on Hydrogen Molecule Ion, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Hydrogen Molecule Ion is topic 97 of 104 in Bonding & Molecular Structure.