key term - He2

Definition

He2 refers to the molecular ion formed by two helium atoms, specifically in its excited state. This molecule is significant in the context of molecular orbital theory as it showcases how helium can form a diatomic molecule under certain conditions, despite helium being a noble gas typically known for its lack of reactivity. Understanding He2 helps illustrate the principles of molecular bonding and electron configuration in diatomic molecules.

5 Must Know Facts For Your Next Test

1. He2 exists primarily as an excited state and is not a stable molecule under standard conditions due to weak bonding interactions.
2. In molecular orbital theory, He2 shows that when two helium atoms combine, they create bonding and antibonding molecular orbitals.
3. The bond order for He2 is calculated as 0, indicating that it does not have a net bonding interaction to support its stability.
4. He2 provides an example of how even noble gases can form transient molecules under specific experimental conditions, like high-energy environments.
5. Molecular orbital theory helps predict the behavior of He2 and other similar molecular ions, showing the importance of electron configurations in determining stability.

Review Questions

• How does He2 illustrate the principles of molecular orbital theory, especially in terms of bonding and antibonding orbitals?
  • He2 illustrates molecular orbital theory by demonstrating how two helium atoms interact to form both bonding and antibonding molecular orbitals. When combining, the electrons from each helium atom occupy these orbitals, leading to the formation of a molecular ion. However, due to having an equal number of electrons in both bonding and antibonding states, He2 has a bond order of 0, which means it does not exhibit a stable bond.
• What role does bond order play in understanding the stability of He2 compared to other diatomic molecules?
  • Bond order is crucial in determining the stability of diatomic molecules like He2. For He2, the bond order is calculated as 0 because there are no net bonding interactions after accounting for both bonding and antibonding electrons. In contrast, other diatomic molecules such as H2 or O2 have positive bond orders, indicating stronger and more stable bonds. This stark difference highlights why He2 is transient and unstable compared to other diatomic species.
• Evaluate the significance of experimental conditions in forming He2 and its implications for understanding noble gases in molecular chemistry.
  • The formation of He2 under specific experimental conditions emphasizes the flexibility of noble gases in molecular chemistry. Typically unreactive due to their full electron shells, helium can momentarily form He2 when subjected to high-energy environments or low temperatures. This situation challenges traditional views about noble gases and showcases how molecular orbital theory can explain transient states that may not be evident under standard conditions. It opens pathways for further research on excited state behavior in other noble gases.

Related terms

Molecular Orbitals:

Regions in a molecule where electrons are likely to be found, formed by the combination of atomic orbitals from bonded atoms.

Bond Order:

A value that indicates the strength and stability of a bond between two atoms, calculated as half the difference between the number of bonding and antibonding electrons.

Diatomic Molecule: A molecule composed of two atoms, which may be of the same or different chemical elements.