Final answer:
The ammonium ion (NH4+) is a unique polyatomic cation, formed from ammonia (NH3) and a hydrogen ion. Its Lewis structure reflects a 1+ charge with a nitrogen atom bonded to four hydrogen atoms.
Step-by-step explanation:
The ammonium ion (NH4+) is a polyatomic ion, which is a group of atoms that are covalently bonded and carry an overall electric charge. In the case of ammonium, a hydrogen ion (H+) forms a coordinate covalent bond with the lone pair of electrons on an ammonia (NH3) molecule. This results in the ammonium ion with a positive charge.
When drawing Lewis structures for polyatomic ions, it is crucial to consider the overall charge for accurately representing the valence electrons. For the ammonium ion, the Lewis structure would show one nitrogen atom covalently bonded to four hydrogen atoms, with no additional electrons, reflecting its 1+ positive charge.
This ion is unique among common polyatomic ions as it is the only cation; the rest, like carbonate or sulfate, are anions, often containing oxygen atoms and known as oxyanions. Correctly identifying these ions, such as nitrate (NO3-) versus nitrite (NO2-), is essential because of their similar formulas and names.