A concern in my basic bromheads.tv textbook gives me a list of formulas because that molecules and also ions. It then asks me come determine, utilizing molecular orbit theory, even if it is or no each would certainly exist in a reasonably stable form.

You are watching: Which electrons in this diagram contribute to the stability of the he2+ ion?

How can I phone call this? The chapter covers molecule shapes, valence bond theory, and molecular orbital theory which all builds on what to be taught in the previous thing (mainly on Lewis structures.) ns can"t phone call what ideas to usage in telling what will certainly be stable and what won"t.


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You need to mix the orbitals, populate them with the electrons and see if you have actually net bonding.

Eg: H + H two 1s orbitals mix to type sigma and also sigma*. Two electrons total, both occupy the sigma orbital, two much more electrons in bonding than antibonding orbitals, the compound is stable.

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Eg: the + He; very same mixing as above. Four electrons, 2 in the sigma, 2 in the sigma*. Since there space as countless bonding electrons together as antibonding, there is no network bond. He2 is not possible.

Eg: he + H; very same mixing as above. 3 electrons, 2 in sigma, one in sigma*. One an ext electron in bonding 보다 antibonding. He-H forms a very weak bond. Please note the diagram is for He2+ yet the He-H is really similar

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Eg: Li + H; Li has actually 1s + 2s, if H has actually 1s. This mix to type a sigma orbital from H1s+Li2s, a sigma* orbital and H1s-Li2s, and a no bonding orbital from Li1s (lower in power than the sigma). Four complete electrons. Nonbonding sigma is occupied, and also then the sigma orbit is occupied. Net effect: Li-H develops a stable bond.

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You can have noticed that the an initial three diagrams had actually identical structure, also if their power levels were different. This is a home of quantum mechanically symmetry, and solving the problem only requires understanding a couple of diagram varieties and filling the electrons in. Think about the 2nd row. The chart is together :

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You simply count the valence electrons and also fill in the diagram. Then you subtract the number of bonding orbit electrons indigenous antibonding, and if you have more, girlfriend will have actually a bond.