Name: Valencies of Some Common Ions
Uploaded: 2019-07-19
Duration: 4 min 56 s
Description: Ionic compounds are composed of positively charged and negatively charged ions. Do you know what the charges on these ions are called? Let’s find out in this...

Question

For the following pairs of elements, deduce the formula and name.

Ammonium ion and sulphite ion

Accepted Answer

Chemical formula of a compound shows its constituent elements and the number of atoms of each combining element. In ionic compounds, the charge on each ion is used to determine the chemical formula of a compound.

Method of writing chemical formula:

Step 1 – write the symbols of constituent ions and their valencies(charges).

Step 2 – write the symbol of cation first followed by the symbol of an anion.

Step 3 – then criss-cross their charges or valencies(lowest possible ratio) to get the formula. When the valency of the both the ions is equal, then subscript is not written.

Step 4 – the positive and negative charges must balance each other and the overall structure must be neutral.

Note : When a compound is formed with polyatomic ions, the ion is enclosed in a bracket before writing the number to indicate the ratio. In case if the number of polyatomic ions is one, the bracket is not required. On the basis of above rules, the chemical formula has been written below.

$\Rightarrow$ Ammonium ion and sulphite ion :

$({NH}_{4} {SO}_{3} + 1 - 2) \Rightarrow {({NH}_{4})}_{2} {SO}_{3}$ (Ammonium sulphite)

For the following pairs of elements, deduce the formula and name.

Ammonium ion and sulphite ion

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