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Carbon has 4 valence electrons, so it means that it can have a total of four (covalent) bonds, correct?

If that's the case, why can't carbon share four bonds, such as with another carbon atom (to form $\ce{C2}$, for example)?

Mithoron
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phi2k
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    The question about fullerenes would probably be best asked as a separate question, with a link back to this one if you really want. – chipbuster Aug 13 '15 at 01:54
  • Have you heard of Valence Bond Theory (orbital hybridization), VSEPR theory, or MO theory? – chipbuster Aug 13 '15 at 01:58
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    I have removed the extra fluff outta your question. We really don't need to know about how you learned about the uncertainty principle. The questions should be free-of-noise and stick to the point. We have [chat] if you want casual conversation with users of the site. – M.A.R. Aug 13 '15 at 05:29

1 Answers1

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s orbitals have spherical symmetry, and p orbitals have a dumb-bell shape. When these orbitals overlap, then they form the bonding orbitals (and corresponding antibonding orbitals). The p-orbitals are aligned along Cartesian (xyz) axes. If all three p-orbitals overlap, then the s-orbitals can't get 'close enough' to overlap and form a fourth bond. If we start mixing s and p orbitals, the geometry always puts electron density away from the other bonding atom.

Concisely: there are no arrangements which allow overlap of atomic orbitals that create four bonding molecular orbitals with the proper orientation.

C2 as a molecule can exist, it will simply only have 3 bonds plus two unpaired electrons confined to each carbon.

If you want a more elaborate answer we have to unpack the heavy quantum mechanics, and you won't be seeing that until your junior year.

Lighthart
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