Question

In the following question, a positive and a negative radical is listed. Using the criss-cross method, write the formula for the compound that is formed and name the compound.

Ag⁺¹ Br^-1

Answer 1

Step-1: Identify the acidic and basic radicals or positive and negative ions:

• Positive ion or cation or basic radical: Ag⁺¹
• Negative ion or anion or acidic radical: Br^-1

Step-2: Write the valency of the ion:

• Valency is written as a positive or negative charge on the ion as a superscript on the right hand side.
• Valency of Ag⁺¹ is 1 Valency of Br^-1 is 1

Step-3: Write the valency of the ion below or above its symbol without the + or - sign:

Symbol of radical Ag Br

Valency of the radical 1 1

Step-4: Transpose the valency by criss-cross:

• Criss-cross multiplication is a method where the valency of a cation is written as a subscript of anion and vice-versa.

$$\begin{gathered} \mathrm{Ag}\mathrm{Br} \\ \searrow \swarrow \\ 11 \end{gathered}$$

Step-5: Write the outcome of criss-cross and simplify by dividing using a common factor if needed

• Ag₁Br₁ or AgBr

Step-6: Write the chemical formula and chemical name

• Cation is written first followed by the anion.
• The chemical formula of the compound is AgBr.
• Name of the cation is written followed by the anion.
• While writing the name of Br^-1, Bromine is changed to Bromide.
• The chemical name of the compound is Silver bromide.