Ammonia is a compound with many unusual properties. The first of these is its unusually high melting point. At -33 degrees Celsius, it’s the most volatile substance in our atmosphere and one of only three chemicals that are liquid at or near room temperature (the others being water and mercury).
But what exactly accounts for ammonia’s strange behavior?
The answer lies in some cool chemistry. An ammonia molecule is made up of three hydrogen atoms and one nitrogen atom. When a single oxygen atom attaches itself to the base ammonium ion, it makes what’s called an amide group (which you can think of as being like bread in that whole “bread goes well with butter” way). The same thing happens when two or more oxygen atoms attach themselves: now we have a polyamide chain.
[In other words,] where there would be just one carbon-oxygen bond between methane molecules for example, [there are now six.] This process also adds bulkiness because these bonds are not straight but rather form zigzags along the long chains. The end result is a polymer network that has increased.