Question

What is the ionic compound formula of ammonium sulfate?

Answer 1

Hint :Sodium sulphate is a white solid powder highly soluble in water. It is usually employed as a fertilizer for the alkaline soils. This compound is generally synthesized by the reaction of sulphuric acid and two equivalents of ammonia.

Complete Step By Step Answer:
As the name suggests, the given compound ammonium sulfate comprises a cationic group and an anionic group of non-metals. We know that any compound containing a cation and an anion is considered to be an ionic compound. In ionic compounds, we have to take into account the charges of each of the elements present in the compound. Now let us identify the formula for the given compound i.e. ammonium sulfate. Ammonium sulfate possesses two polyatomic ions (i.e. group of nonmetals (ammonium and sulfate in this case) so we'll use a table of names for the common polyatomic ions, along with the Periodic Table. Rules to write formula of a ternary ionic compound are listed below:
1. Using the periodic table, write down the symbol for the element along with its charge.
In the present case, we have polyatomic ions which are not available in periodic tables.
2. Using the Common ion table, identify the symbol as well as charge of the polyatomic ions.
In the present case, polyatomic ion ammonium is written as $ N{H_4} $ having a charge +1 and sulfate is written as $ S{O_4} $ having a charge -2.
3. Check if the charges are balanced
In the present case it becomes $ NH_4^{1 + }SO_4^{2 - } $ . The charges are not balanced as summation of charges is non-zero i.e. $ ( + 1) + ( - 2) = - 1 \ne 0 $
4. If unbalanced charges are there, add subscripts following the criss-cross method such that net charge for the compound is zero.
In the present case, we will add subscripts to each polyatomic ion such that the net charge becomes zero. So it becomes $ {(NH_4^{1 + })_2}{(SO_4^{2 - })_1} $ and now the net charge is balanced i.e. $ (2 \times ( + 1)) + (1 \times ( - 2)) = 0 $
Hence, the ionic compound formula for Ammonium sulfate is $ {(N{H_4})_2}S{O_4} $ .

Note :
While writing the chemical formula of an ionic compound, never write the subscript '1'. Always remember that we can also have two polyatomic ions in the same compound as it is in the present case. In this case, we always have to find and write both of the names as identified from the Common Ion Table instead of periodic table.