Question

Urea is an important chemical fertilizer with the chemical formula $\left(H_{2}N\right)\mathbf{CO}\left({\mathrm{NH}}_2\right)$. The carbon atom is bonded to both nitrogen atoms and the oxygen atom. Draw a Lewis diagram for urea and use Table 3.6to estimate its bond lengths.

Short answer

The Lewis diagram for the urea is:

Step-by-step solution

Lewis structure

Most of the bonds and lone pairs are direct consequences of the rules of assigning electrons. The $\mathrm{C}=\mathrm{O}$double bond needs to be added to reach tetravalency on carbon and to reduce charges in the structure. (Otherwise, oxygen would be -1 and carbon would be +1 if there is only a single bond between them.)

Bond lengths

All of the corresponding average bond lengths are included in the textbook table:

• N-H single bond$1.01{\mathrm{A}}^0$
• C-N single bond$1.47{\mathrm{A}}^0$
• $\mathrm{C}=\mathrm{O}$double bond$1.20{\mathrm{A}}^0$

Note that these average lengths are just estimates in case of a given molecule. The units${\mathrm{A}}^0$ are equal to${10}^{-10}$ meters.