Nitrogen, ammonia and ammonium salts
Connect atmospheric N2 to NH3, NH4+ and the nitrogen cycle.
Learning goals: explain why N2 is stable; describe ammonia geometry, preparation and basic behavior; identify ammonium ions; trace fixation, nitrification, uptake and denitrification; apply safe handling.
1. Nitrogen molecule and reactivity
Nitrogen is a group 15 nonmetal with five valence electrons. In N2, two atoms share three electron pairs, forming a short, strong triple covalent bond. This bond makes molecular nitrogen relatively unreactive at ordinary conditions even though nitrogen atoms can form many compounds. Nitrogen shows oxidation states from −3 in NH3 to +5 in nitrate. Most atmospheric nitrogen is N2, but organisms need chemically available forms such as ammonium or nitrate.