0.4 Chemical bonding  (Page 2/9)

A nitrogen atom has 7 electrons, and an electron configuration of $1\mathrm{s}{}^{2}2\mathrm{s}{}^{2}2\mathrm{p}{}^3$ . A hydrogen atom has only 1 electron, and an electron configuration of $1\mathrm{s}{}^1$ .

Nitrogen has 5 valence electrons meaning that 3 electrons are unpaired. Hydrogen has 1 valence electron and it is unpaired.

Each hydrogen atom needs one more electron to complete its valence energy shell. The nitrogen atom needs three more electrons to complete its valence energy shell. Therefore three pairs of electrons must be shared between the four atoms involved. The nitrogen atom will share three of its electrons so that each of the hydrogen atoms now have a complete valence shell. Each of the hydrogen atoms will share its electron with the nitrogen atom to complete its valence shell ( [link] ).

Each oxygen atom has 8 electrons, and their electron configuration is $1\mathrm{s}{}^{2}2\mathrm{s}{}^{2}2\mathrm{p}{}^4$ .

Each oxygen atom has 6 valence electrons, meaning that each atom has 2 unpaired electrons.

Each oxygen atom needs two more electrons to complete its valence energy shell. Therefore two pairs of electrons must be shared between the two oxygen atoms so that both valence shells are full. Notice that the two electron pairs are being shared between the same two atoms, and so we call this a double bond ( [link] ).