Nitrogen acidic salt or weak base?

[Jolie 3H]

Hi! I am confused about 2 concepts about nitrogen in this unit. We talked about how a nitrogen species with lone pair is a weak base. We also talked about how a nitrogen with H in a salt makes the salt acidic. Could someone please explain how these two concepts are different and yields different properties in acidity/basicness?

[Angel Shen 2K]

Hi,
I don't think you should look for patterns but rather understand the concept behind how things behave they do. When nitrogen has a lone pair, like in ammonia it acts as a weak base because it can accept protons. This makes it basic in nature. On the other hand, when nitrogen is part of an ammonium ion NH4+, it can donate a proton, making it acidic. The ammonium ion dissociates in water, releasing H+ ions, which lowers the pH and makes the solution acidic. So, the key difference is that nitrogen with a lone pair is basic because it accepts protons, while nitrogen in the ammonium form is acidic because it donates protons. Hope this helps!