To draw the Lewis structure for ammonia (NH3), we start by determining the total number of valence electrons available. Nitrogen, being in group 15 of the periodic table, has 5 valence electrons, and each hydrogen atom, being in group 1, has 1 valence electron. Since there are three hydrogen atoms, we have:
- 1 Nitrogen: 5 valence electrons
- 3 Hydrogen: 3 valence electrons (1 electron each)
This gives us a total of:
5 + 3 = 8 valence electrons.
Next, we place the nitrogen atom in the center, as it is less electronegative than hydrogen. Then, we surround it with the three hydrogen atoms. Each hydrogen will form a single bond with nitrogen, which uses 6 of the total 8 electrons (2 electrons per bond).
The remaining 2 electrons will then be placed as a lone pair on the nitrogen atom. Therefore, the Lewis structure for ammonia is represented as:
H
|
H - N :
|
H
In this structure, the nitrogen atom has one lone pair and shares one pair of electrons with each hydrogen, fulfilling the octet rule for nitrogen and the duet rule for hydrogen.