Multiple covalent bonds are formed when atoms share more than one pair of electrons to achieve a stable electron configuration. This typically happens when single covalent bonds aren't sufficient for atoms to satisfy the octet rule (or duet rule for hydrogen).
Understanding Covalent Bonds
A covalent bond is formed when atoms share electrons, as opposed to transferring them (ionic bonding). The shared electrons are attracted to the nuclei of both atoms, holding them together.
Single, Double, and Triple Bonds
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Single Covalent Bond: One pair of electrons (2 electrons) is shared between two atoms.
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Double Covalent Bond: Two pairs of electrons (4 electrons) are shared between two atoms. An example is oxygen gas (O=O) where each oxygen atom shares two electrons with the other.
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Triple Covalent Bond: Three pairs of electrons (6 electrons) are shared between two atoms. A common example is nitrogen gas (N≡N) where each nitrogen atom shares three electrons with the other.
Why Multiple Bonds Form
Atoms form multiple bonds to achieve a stable valence electron configuration, resembling that of a noble gas. For example:
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Carbon: Carbon has four valence electrons and needs four more to achieve an octet. It can form four single bonds, two double bonds, one triple bond and one single bond, or one double bond and two single bonds to fulfill this requirement.
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Nitrogen: Nitrogen has five valence electrons and needs three more. It often forms a triple bond to another nitrogen atom or a combination of single and double bonds with other atoms.
Examples of Multiple Covalent Bonds
| Molecule | Type of Bond | Lewis Structure (Simplified) |
|---|---|---|
| Oxygen (O2) | Double | O=O |
| Carbon Dioxide (CO2) | Double | O=C=O |
| Nitrogen (N2) | Triple | N≡N |
| Ethyne (C2H2) | Triple | H-C≡C-H |
| Ethene (C2H4) | Double | H2C=CH2 |
Characteristics of Multiple Bonds
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Strength: Multiple bonds are generally stronger than single bonds because they involve more shared electrons. A triple bond is stronger than a double bond, which is stronger than a single bond.
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Length: Multiple bonds are shorter than single bonds. The more electrons shared, the stronger the attraction between the atoms, and the closer they are pulled together.
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Reactivity: Multiple bonds can be more reactive than single bonds because the electrons in pi bonds (present in double and triple bonds) are more exposed and easier to attack by other molecules.
In summary, multiple covalent bonds form when atoms share more than one pair of electrons to achieve a stable octet (or duet) configuration, resulting in stronger and shorter bonds compared to single covalent bonds.
