The valency of sulphide and oxide ions is:

• a. -2
• b. -3
• c. -4
• d. -5

The valency of ions is an important concept in chemistry, as it helps us understand how different elements combine to form compounds. In the case of sulphide and oxide ions, both have a specific charge that indicates their valency. Let's break this down for clarity.

Understanding Ion Charges

Valency refers to the ability of an atom to bond with other atoms, often determined by the number of electrons an atom can gain, lose, or share. For ions, this is represented by their charge. The sulphide ion (S²⁻) and the oxide ion (O²⁻) are both negatively charged ions, known as anions.

Sulphide Ion (S²⁻)

The sulphide ion carries a charge of -2. This means that it has gained two electrons compared to its neutral state. In terms of bonding, this allows sulphide to combine with positively charged ions (cations) that have a charge of +2 or less to form stable compounds, such as in metal sulfides.

Oxide Ion (O²⁻)

Similarly, the oxide ion also has a charge of -2. Like sulphide, it has gained two electrons, making it capable of forming bonds with cations that can balance this charge. For example, when oxygen combines with metals, it often forms metal oxides, where the metal cation balances the -2 charge of the oxide ion.

Comparative Analysis of Valency

Both sulphide and oxide ions share the same valency of -2. This is crucial when predicting how these ions will interact with other elements in chemical reactions. For instance, when forming compounds, the total positive charge from cations must equal the total negative charge from anions to maintain electrical neutrality.

• Example of Sulphide: In iron(II) sulfide (FeS), iron has a +2 charge, which balances the -2 charge of the sulphide ion.
• Example of Oxide: In magnesium oxide (MgO), magnesium has a +2 charge, which balances the -2 charge of the oxide ion.

In summary, both the sulphide and oxide ions have a valency of -2. This understanding is fundamental in predicting how these ions will interact in various chemical contexts, forming stable compounds through ionic bonding.