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| Polar and Non-Polar Covalent Bonds |
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| Covalent bonds may be non-polar or polar in nature. |
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| Differences between non-polar and polar covalent compounds |
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| Methane |
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| The shared pair is equidistant from both carbon and hydrogen atoms. Neither the carbon atom, nor the hydrogen atom can pull the shared pair towards itself as there is little difference [carbon = 2.5ev, hydrogen = 2.1ev] in their electronegativities. |
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| Hydrogen chloride is a polar molecule. Hydrogen atoms shares one electron with chlorine atom to complete its octet. Chlorine on the other hand has seven valence electrons, it needs one more to complete its octet. Chlorine has an electronegativity of three, while hydrogen atom has a electronegativity of 2.1ev. |
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| Therefore, chlorine atom pulls the shared pair towards itself acquiring a slight -ve charge represented by d-. Hydrogen gets a slight positive charge, d+. |
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| In the ammonia molecule, there are three hydrogen atoms and one nitrogen atom. |
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| A nitrogen atom has five valence electrons, it needs three more electrons to complete its octet. It forms three single bonds with three hydrogen atoms. Nitrogen completes its octet while hydrogen completes its duplet. The nitrogen atom still has two valence electrons which are not involved in bonding they are called the lone pair of electrons. |
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| Nitrogen is more electronegative than hydrogen, therefore the electron pair shifts towards nitrogen. The nitrogen atom acquires a slight negative charge (d-) and hydrogen atoms a slight positive charge (d+). |
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| The lone pair of electrons provides special properties to the compound. In ammonia, the basic nature is attributed to the lone pair. In water the oxygen atoms has 2 lone pair of electrons. These account for water being a universal solvent. |
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