Consider the H2+ ion. (e) Suppose that the ion is excited by light so that an electron moves from a lower-energy to a higher-energy MO. Would you expect the excited-state H2+ ion to be stable or to fall apart?

Verified step by step guidance

1. Identify the molecular orbitals (MOs) of the H2+ ion. In H2+, there are two key molecular orbitals to consider: the bonding molecular orbital (σ1s) and the antibonding molecular orbital (σ*1s).
2. Understand the electron configuration of the ground state and the excited state of H2+. In its ground state, the single electron of H2+ occupies the lower energy σ1s orbital. When excited by light, the electron transitions to the higher energy σ*1s orbital.
3. Analyze the stability of the molecular orbitals. The bonding orbital (σ1s) has a lower energy and contributes to the stability of the molecule by lowering the overall energy. In contrast, the antibonding orbital (σ*1s) has higher energy and tends to destabilize the molecule.
4. Consider the effect of the electron in the antibonding orbital. With the electron in the σ*1s orbital, the electron density between the nuclei decreases, reducing the attractive forces that hold the nuclei together and increasing the repulsive forces.
5. Conclude on the stability of the excited-state H2+ ion. Given that the electron in the excited state occupies an antibonding orbital, which destabilizes the molecule, it is likely that the excited-state H2+ ion would be less stable and could potentially dissociate or fall apart.

Key Concepts

Molecular Orbitals (MOs)

Molecular orbitals are regions in a molecule where electrons are likely to be found. They are formed from the combination of atomic orbitals and can be classified as bonding, antibonding, or non-bonding. In the case of H2+, the bonding molecular orbital is lower in energy and stabilizes the molecule, while the antibonding orbital is higher in energy and can destabilize it if occupied.

Excitation of Electrons

When an electron absorbs energy, such as from light, it can be promoted from a lower-energy molecular orbital to a higher-energy one. This process is known as excitation. In the context of H2+, if an electron is excited to a higher-energy molecular orbital, it may lead to changes in the stability of the ion, potentially making it less stable.

Stability of Ions

The stability of ions, such as H2+, depends on the balance between attractive and repulsive forces within the molecule. If an electron is excited to a higher-energy state, it may occupy an antibonding orbital, which can weaken the bond between the hydrogen nuclei. This can lead to the ion becoming unstable and potentially dissociating into separate hydrogen atoms.