| 11. | Bonding in such clusters is often discussed in the context of polyhedral skeletal electron pair theory.
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| 12. | The electron pairs dominate the repulsions, and the tiny H atoms are insignificant in this respect.
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| 13. | When the electron pair moves towards the attacking reagent, it is termed as the + E effect.
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| 14. | High-energy gamma rays, upon striking the upper atmosphere, can create positron-electron pairs that move at great speeds.
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| 15. | The four electron pairs are spread so as to point roughly towards the apices of a tetrahedron.
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| 16. | This property makes them both excellent nucleophiles " and " lewis bases ( electron pair doners ).
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| 17. | However, they are Lewis acids, because they accept electron pairs from some Lewis bases, most notably base anhydrides.
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| 18. | The electron pairs can therefore be described as having a distorted tetrahedral geometry, but the molecule is pyramidal.
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| 19. | In short, a compounds is an acid because it donates a proton ( accepts an electron pair ).
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| 20. | If they are not, the remainder will form non-bonding electron pairs, usually known as " lone pairs ".
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