Jack asked in Science & MathematicsChemistry · 1 decade ago

"Predict the polarity of the covalent bonds..."?

Predict the polarity of the covalent bonds in the following molecules, using the notation o+ and o- where appropriate.

2 questions..

a) HF

b) N2

Ok, I have never done this before (first year of 6th form (chemistry)) and I don't have a clue what polarity is. Can someone please explain what it means/does and perhaps answer my first 2 questions as examples? :D

Looking for a quick answer as this homework is in for tomorrow!

3 Answers

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  • 1 decade ago
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    Polarity occurs when the electronegativities of the two atoms bonded together have a larger discrepancy. I believe the standard is: If the electronegativity DIFFERENCE is between 0.3 and 2.0, then the bond is polar covalent meaning the more electronegative atom "hogs" the electrons most of the time.

    Use a table with electronegativities (like this one: http://www.tutor-homework.com/Chemistry_Help/elect... ). You'll see that the difference between HF is somewhere in that range (i.e. take the electronegativity of Fluorine and subtract it from that of Hydrogen). HF is indeed polar covalent. Draw delta+ over the hydrogen and delta- over the fluorine.

    Any diatomic elements will automatically have an electronegativity difference of zero, making them non-polar covalent, such as N2, O2, Cl2, etc.

    Anything with an electronegativity difference higher than 2.0 is ionic.

  • Anonymous
    1 decade ago

    All atoms have a specific electronegativity, which means that all atoms have a specific "amount" of ability to attract electrons to themselves from OTHER neighbooring atoms in the molecule!

    For example, HF (hydrofluoric acid) is a molecule, that contains two atoms: a hydrogren atom, and a fluorine atom. Hydrogen's specific electronegativity is 2.2, and fluorine's specific electronegativity is 4.0 ...which is the highest electronegativity that any atom has! So, since fluorine is more electronegative than hydrogen, the electrons in the H-F bond will be attracted to, and closer to the fluorine atom! Hence, the HF molecule is polar (the atoms in the molecule have a difference in electronegativity!)

    N2 is basically two nitrogen atoms with a single bond between them like this: N-N

    A nitrogen atom has a specific electronegativity. But N2 is a NONpolar molecule because the two nitrogen atoms have the same electronegativity! There is no difference in electronegativity! So, N2 molecule is nonpolar!

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