5.3 Radicals and Their Valencies

• Definition of Radicals: Radicals are groups of atoms from different elements that combine together, gain positive or negative charges, and act as ions of elements. They can be positively or negatively charged and are referred to as “radicals” or “ions.”

• Charge and Valency: The charge of a radical determines its valency.

• A positive charge indicates a positive valency.

• A negative charge indicates a negative valency.

• Valency is the magnitude of the charge (the number only, without the sign).

Example:

• The Ammonium ion (NH4+) consists of three hydrogen atoms and one H+ ion combined with one nitrogen (N) atom. Since its charge is +1, its valency is also 1.

• Radicals and Their Valencies:

Radical Formula Charge Valency

Ammonium NH4+ +1 1

Carbonate CO3^2- -2 2

Hydrogen Carbonate HCO3- -1 1

Sulfate SO4^2- -2 2

Hydrogen Sulfate HSO4- -1 1

Sulfite SO3^2- -2 2

Nitrate NO3- -1 1

Nitrite NO2- -1 1

Phosphate PO4^3- -3 3

Hydroxide OH- -1 1

Phosphonium PH4+ +1 1

• Explanation:

• Radicals like Ammonium (NH4+) and Phosphonium (PH4+) have a positive charge of +1, so their valency is 1.

• Carbonate (CO3^2-) and Sulfate (SO4^2-) have a negative charge of -2, so their valency is 2.

• Phosphate (PO4^3-) has a negative charge of -3, so its valency is 3.

• Conclusion:

• Radicals are ionized groups of atoms that behave like single elements in reactions.

• The charge of a radical directly determines its valency, and this valency helps in understanding how radicals combine with other atoms or molecules to form compounds.