Question

What is the Lewis structure for `CN_2H_2`?

Answer 1

In order to determine the Lewis structure of methanediimine, or `CN_2H_2`, you must first determine the molecule's total number of valence electrons.

This is done by adding the valence electrons of each of the atoms that form the molecule

`4 * (1) + 2 * (5) + 2 * (1) = "16e"^(-)`

Carbon contributes 4 valence electrons, each of the nitrogen atom acontributes 5, and each of the hydrogen atoms contributes 1 valence electron.

So, start by connecting all the atoms with single bonds.

http://chem-net.blogspot.ro/2012/11/construction-of-lewis-electron-dot.html

Each single bond has 2 electrons, so we've used up `4 * 2 = 8` valence electrons. Now focus on giving the carbon atom a full octet.

http://chem-net.blogspot.ro/2012/11/construction-of-lewis-electron-dot.html

Now you only have to work with `4` valence electrons, since `12` have been used up already. Give the two nitrogen atoms full octets as well by placing a lone pair of electrons on each atom

http://chem-net.blogspot.ro/2012/11/construction-of-lewis-electron-dot.html

This will complete the Lewis structure of the molecule, since all `16` valence electrons are placed on the molecule.