Question

Supply a systematic name for each of the following binary ionic compounds: (a) \(\mathrm{MgO}\) (b) \(Z n O\) (c) \(\mathrm{CdO}\) (d) \(\mathrm{BaO}\)

Short answer

(a) Magnesium oxide, (b) Zinc oxide, (c) Cadmium oxide, (d) Barium oxide.

Step-by-step solution

Identify Cation and Anion in Compound

For each compound, identify the metal (cation) and the non-metal (anion). The metal is listed first followed by the non-metal oxide ion.

Name the Metal (Cation)

The systematic name for the cation is simply the name of the metal. All metals listed here form only one type of ion with a consistent charge.

Combine Name of Cation with 'Oxide'

The non-metal ion in each case is the oxide ion, \( ext{O}^{2-}\). Therefore, for the anion, use the term 'oxide' to form the name of the compound by combining with the cation name.

Key concepts

Binary Ionic Compounds

Binary ionic compounds are composed of exactly two elements: one metal and one non-metal. These elements come together to form a compound through ionic bonds. The metal atom, which loses electrons, becomes a positively charged ion known as a cation. On the other hand, the non-metal atom gains these electrons and becomes a negatively charged ion, known as an anion. When naming binary ionic compounds, you first list the metal and then the non-metal. For example, in compounds like \( \mathrm{MgO} \) or \( \mathrm{BaO} \), magnesium and barium are metals that combine with the non-metal oxygen. The charge-balancing process is crucial: the positive charges from the metal cations counterbalance the negative charges from the oxide ions to achieve electrical neutrality.

Cation and Anion Identification

Identifying the cation and anion in a compound is a fundamental step in naming binary ionic compounds systematically. The cation always comes from the metal, while the anion comes from the non-metal. In our given examples:- \( \mathrm{MgO} \) contains magnesium (cation) and oxide (anion).- \( \mathrm{ZnO} \) has zinc as the cation and oxide as the anion.- \( \mathrm{CdO} \) includes cadmium for the cation and oxide as the anion.- \( \mathrm{BaO} \) has barium as the cation and oxide as the anion.Beginners often identify them by the position in the chemical formula, with metals typically first.

Naming Metal Cations

When naming metal cations, the systematic name is straightforward. For metals like magnesium, zinc, cadmium, and barium, the ion name is the same as the element name. This is because these metals form only one type of stable ion with a specific positive charge:

• Magnesium forms \( \mathrm{Mg^{2+}} \)
• Zinc forms \( \mathrm{Zn^{2+}} \)
• Cadmium forms \( \mathrm{Cd^{2+}} \)
• Barium forms \( \mathrm{Ba^{2+}} \)

Because of this, there is no need for Roman numerals indicating charge in the naming process, simplifying the naming of these metal cations in compounds.

Oxide Ions in Compounds

The term "oxide ion" refers to oxygen in its ionic form, \( \text{O}^{2-} \). When it forms a compound with metals, it acts as the anion. Oxide ions are quite common because oxygen is a prevalent and reactive non-metal. In each of our given examples, oxygen combines with different metals to form:

• Magnesium oxide: \( \mathrm{MgO} \)
• Zinc oxide: \( \mathrm{ZnO} \)
• Cadmium oxide: \( \mathrm{CdO} \)
• Barium oxide: \( \mathrm{BaO} \)

In each instance, the ionic bond balances out, with the \( \text{O}^{2-} \) neutralizing the charge of the \( \text{M}^{2+} \) metal cation, seamlessly forming stable binary ionic compounds.