Which sequence correctly lists the chemical symbols for nitrite, nitrate, unionized ammonia, and ionized ammonia?

Which sequence correctly lists the chemical symbols for nitrite, nitrate, unionized ammonia, and ionized ammonia?

• A. NO3-, NH3, NH4+, NO2-
• B. NO2-, NO3, NH3, NH4+
• C. NO3-, NH3, NH4+, CO2
• D. NH3, NH4+, NH2, NH5

Answer: (B)

Recognizing the distinct chemical forms and their charges for nitrogen species and ammonia is what this question tests. Nitrite is the two-oxygen ion NO2-; nitrate is the three-oxygen ion NO3- (both carry a -1 charge). Unionized ammonia is NH3, a neutral molecule. Ionized ammonia is NH4+, the ammonium ion formed when NH3 gains a proton and becomes positively charged. The requested sequence—nitrite, nitrate, unionized ammonia, ionized ammonia—maps to NO2-, NO3-, NH3, NH4+. While nitrate is usually written NO3- in formal notation, the symbol NO3 is commonly understood in many contexts, and this order correctly reflects the progression of these species.

Recognizing the distinct chemical forms and their charges for nitrogen species and ammonia is what this question tests. Nitrite is the two-oxygen ion NO2-; nitrate is the three-oxygen ion NO3- (both carry a -1 charge). Unionized ammonia is NH3, a neutral molecule. Ionized ammonia is NH4+, the ammonium ion formed when NH3 gains a proton and becomes positively charged. The requested sequence—nitrite, nitrate, unionized ammonia, ionized ammonia—maps to NO2-, NO3-, NH3, NH4+. While nitrate is usually written NO3- in formal notation, the symbol NO3 is commonly understood in many contexts, and this order correctly reflects the progression of these species.