What is the correct chemical formula of ammonium nitrate, a commonly used nitrogenous fertiliser?

Introduction / Context:
This question focuses on the formula of ammonium nitrate, an important inorganic compound used as a nitrogen rich fertiliser and in some industrial applications. Knowing the correct formula is useful in agricultural chemistry, environmental studies and general science examinations that test familiarity with common fertilisers and their compositions.

Given Data / Assumptions:

• We are asked for the chemical formula of ammonium nitrate.
• Options propose several possible combinations of ammonium and nitrate ions.
• We assume standard ionic composition where ammonium is NH4+ and nitrate is NO3-.

Concept / Approach:
Ammonium nitrate is an ionic compound formed from the ammonium cation, NH4+, and the nitrate anion, NO3-. The charges on NH4+ and NO3- are plus one and minus one respectively, so they combine in a one to one ratio to form a neutral compound. Therefore, the formula is NH4NO3. Any formula that suggests different ratios or different ions does not correctly represent ammonium nitrate.

Step-by-Step Solution:
Step 1: Identify the ions involved. Ammonium ion is NH4+ and nitrate ion is NO3-. Step 2: Ammonium has charge plus one, nitrate has charge minus one. Step 3: To form a neutral ionic compound, one NH4+ ion combines with one NO3- ion. Step 4: Therefore, the formula of the compound is NH4NO3. Step 5: Check option B, NH4NO3, which matches this simple one to one combination. Step 6: Option A, (NH2)2NO3, suggests different ions and does not correspond to ammonium nitrate. Step 7: Option C, NH4(NO3)2, would indicate two nitrate ions per ammonium ion, leading to a net negative charge and not a neutral formula. Step 8: Option D, NH2NO3, does not represent a standard ammonium salt and has incorrect hydrogen count for ammonium. Step 9: Option E, NH4NO2, is ammonium nitrite, which is a different compound with the nitrite ion NO2- instead of nitrate.

Verification / Alternative check:
Agricultural and chemistry references list ammonium nitrate as NH4NO3, emphasising that it provides nitrogen in both ammonium and nitrate forms, which are usable by plants. The compound is also known from news reports about fertiliser use and storage, always with the same formula. Remembering that ammonium nitrate is the ammonium salt of nitric acid can also help, because nitric acid has formula HNO3, and replacing the hydrogen with ammonium gives NH4NO3.

Why Other Options Are Wrong:
Formulas such as (NH2)2NO3 or NH2NO3 do not correctly reflect the ammonium ion NH4+. NH4(NO3)2 suggests a doubly charged nitrate combination, which is not typical for a neutral salt. NH4NO2 is a real compound but it is ammonium nitrite, not nitrate, and has different properties and uses. Thus, these alternatives do not meet the requirement of being ammonium nitrate.

Common Pitfalls:
A common confusion is between nitrate and nitrite ions, NO3- and NO2-. Always check the number of oxygen atoms when writing formulas. Another pitfall is to overcomplicate the formula by adding extra ions or parentheses when a simple one to one pairing is sufficient. Remember that ammonium nitrate is one of the simplest ammonium salts in terms of stoichiometry, with NH4+ and NO3- combining directly.

Final Answer:
The correct chemical formula of ammonium nitrate is NH4NO3.