Examples: SO 4 2-, N 2 O, XeO 3; Notable Exceptions to the Octet Rule. H only needs 2 valence electrons. Be and B don’t need 8 valence electrons. S and P sometimes have more than 8 val. Elements in Period Three, Four, etc (on the periodic table) can hold more than 8 valence electrons. For example, in above, Helium (He) and Neon (Ne) have outer valence shells that are completely filled, so neither has a tendency to gain or lose electrons. Therefore, Helium and Neon, two of the so-called Noble gases, exist in free atomic form and do not usually form chemical bonds with other atoms.
Lewis Structures are important to learn because they help us predict:
- the shape of a molecule.
- how the molecule might react with other molecules.
- the physical properties of the molecule (like boiling point, surface tension, etc.).
That helps us understand and predict interactions with things like medicine and our body, materials used to make buildings and airplanes, and all sorts of other substances. Lewis structures don't tell us everything, but along with molecule geometry and polarity they are hugely informative.
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Where Are Valence Electrons Found
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Advanced Steps Notable Exceptions to the Octet Rule
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