Arrange the following points in sequence for derivation of formulae of compounds

i) The valencies of the ions or radicals are written below the radicals without positive and negative sign

ii) If the valencies have common factors, they are divided by the highest common factor

iii) The magnitude of valencies should be interchanged and written as subscripts on the right side of the respective ions.

iv) The positive radical followed by negative radical are written with their charges

v) If the radicals contain more than one atom, they are enclosed in brackets and the appropriate valency (more than one) written as subscripts outside the bracket.

iv, i, ii, iii, v

Here's a breakdown of the steps and why this order is correct:

1. Identify the ions or radicals and their charges:

• Step iv: This step is crucial as it establishes the basic framework of the compound. We need to know which ion is positive and which is negative to correctly determine their positions in the formula.

2. Write the valencies:

• Step i: Once we know the ions, we write their valencies (without the positive or negative signs) below them. This helps us understand the combining capacity of each ion.

3. Simplify the valencies (if necessary):

• Step ii: If the valencies have a common factor, we divide both by the highest common factor. This simplifies the formula and ensures the smallest possible subscripts.

4. Interchange valencies and write as subscripts:

• Step iii: This is the core step of formula derivation. We interchange the valencies and write them as subscripts on the opposite ions. This ensures that the total positive charge equals the total negative charge in the compound.

5. Enclose polyatomic ions in brackets (if needed):

• Step v: If a radical (polyatomic ion) contains more than one atom, we enclose it in brackets to indicate that the subscript applies to the entire group of atoms. This is important to avoid ambiguity.

Example:

Let's derive the formula for sodium chloride (NaCl):

1. Identify ions: Sodium (Na+) and Chloride (Cl-)
2. Write valencies: Na⁺¹ Cl⁻¹
3. Simplify valencies: No common factor, so we proceed.
4. Interchange valencies: Na₁Cl₁
5. Write the formula: NaCl

By following these steps in the given order, we can accurately derive the formula for any compound.