How does nitrogen bond with itself to form N2 if it has no affinity for electrons? If a nitrogen atom can't pull on the electrons of another nitrogen atom how can N2 have covalent bonds.
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2$\begingroup$ Why do you say Nitrogen Atoms have no affinity of electrons? $\endgroup$– IT TsoiMay 30, 2016 at 13:25
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$\begingroup$ Covalent bonding is not about electron affinity at all. It is about two atoms getting together and creating molecular orbitals, some of which are lower in energy than the starting atomic orbitals, so the electrons may happily go there. It is a win-win situation. $\endgroup$– Ivan NeretinJun 1, 2016 at 10:09
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1 Answer
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It doesn't matter that the electronegativity difference between nitrogen with itself is 0. It just means the bonds it makes with another nitrogen atom have $100~\%$ covalent character.
A typical chemical bond basically spans the spectrum of bonds with $100~\%$ ionic character, uneven ionic/covalent character, and $100~\%$ covalent character.
$\mathbf{100~\%}$ ionic character: $\ce{A^+B^-}$ or $\ce{A^- B^+}$, with no sharing of electrons at all
Uneven ionic/covalent character (i.e. polar): $\ce{{\stackrel{\delta+}{A}}-{\stackrel{\delta-}{B}}}$ or $\ce{{\stackrel{\delta-}{A}}-{\stackrel{\delta+}{B}}}$, with deviation from perfect sharing of electrons and direction of favored negative/positive end of dipole determined by electronegativity difference
$\mathbf{100~\%}$ covalent character (i.e. $100~\%$ nonpolar): $\ce{A-A}$ or $\ce{B-B}$, with perfect sharing of electrons
It just so happens that $\ce{N2}$ is one example of $100~\%$ covalent character. You can argue the same for $\ce{O2}$, and any similar homonuclear diatomic molecule.
(Granted, there are some exceptions to 100% covalent character, like in iron's metallic bonding, but anyways...)
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$\begingroup$ I’ll respectfully disagree with the first paragraph. I wouldn’t consider metallic bonding as in iron and covalent bonding entirely equivalent, but otherwise nice answer. $\endgroup$– JanMay 31, 2016 at 9:39
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$\begingroup$ Well, I've personally never heard of $Fe_2$. I have heard of iron making an $Fe-Fe$ bond, though, like in diiron octacarbonyl. :) $\endgroup$ Jun 1, 2016 at 18:30
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$\begingroup$ But I was referring to elemental, solid $\unicode[Times]{x3b1}$-iron ;) Technically, these are very extended bonds. $\endgroup$– JanJun 1, 2016 at 18:43