Using MO theory (but w.o drawing a MO diagram) predict whether HHe or HHe+ would be more stable.
I believe HHe+ would be more stable as the bond order would be 1 (i.e. BO=(2-0)/2) while BO for HHe is 1/2.
Please confirm! thanks!
To predict the relative stability of HHe and HHe+ using MO theory without drawing a MO diagram, you can consider the following principles:
1. Bond Order: Bond order is a measure of the stability and strength of a bond. It is calculated as the difference between the number of bonding electrons and the number of antibonding electrons in a molecule, divided by 2. Higher bond order generally indicates greater stability.
2. Ionization Energy: Ionization energy is the energy required to remove an electron from an atom or ion. Higher ionization energy indicates greater stability for an ion.
Based on these principles, let's analyze HHe and HHe+:
1. HHe: In molecular bonding, hydrogen (H) has one valence electron and helium (He) has two valence electrons. When they combine, they form a sigma molecular orbital (sigma MO) and a sigma* antibonding orbital (sigma* MO). Since there are two electrons in the bonding MO and none in the antibonding MO, the bond order is 1/2 [(2-0)/2].
2. HHe+: When a hydrogen atom donates its electron to helium ion (He+), the resulting ion has a helium atom with only one electron. Since He+ only has one valence electron, it has a bond order of 1 [(2-1)/2]. The ionization energy required to remove an electron from the helium ion is relatively high due to the strong attraction of the helium nucleus for its lone electron.
Considering the bond order and ionization energy, it can be predicted that HHe+ is more stable than HHe. This is because HHe+ has a higher bond order (BO = 1) compared to HHe (BO = 1/2) and higher ionization energy, indicating greater stability for the ion.
Thus, your prediction that HHe+ is more stable than HHe is correct.