Question

Write the chemical formula for the following ternary compounds given their constituent ions: (a) lead(IV) sulfate, \(\mathrm{Pb}^{4+}\) and \(\mathrm{SO}_{4}{ }^{2-}\) (b) stannous chlorite, \(\mathrm{Sn}^{2+}\) and \(\mathrm{ClO}_{2}^{-}\) (c) cobalt(II) hydroxide, \(\mathrm{Co}^{2+}\) and \(\mathrm{OH}^{-}\) (d) mercurous phosphate, \(\mathrm{Hg}_{2}{ }^{2+}\) and \(\mathrm{PO}_{4}{ }^{3-}\)

Short answer

(a) \(\mathrm{Pb(SO}_{4})_{2}\), (b) \(\mathrm{Sn(ClO}_{2})_{2}\), (c) \(\mathrm{Co(OH)_{2}}\), (d) \(\mathrm{Hg}_{2}_{3}(\mathrm{PO}_{4})_{2}\).

Step-by-step solution

Understanding Ternary Compounds

Ternary compounds are composed of three different elements, often involving a metal ion and a complex ion (like sulfate, chlorite, or phosphate). To write the formula, we must balance the charges between these ions.

Write the Formula for Lead(IV) Sulfate

Lead(IV) has a charge of +4 (\(\mathrm{Pb}^{4+}\)), and sulfate has a charge of -2 (\(\mathrm{SO}_{4}^{2-}\)). To balance the overall charge, we need two sulfate ions for every lead ion. Therefore, the formula is \(\mathrm{Pb(SO}_{4})_{2}\).

Write the Formula for Stannous Chlorite

Stannous refers to tin with a +2 charge (\(\mathrm{Sn}^{2+}\)), and chlorite has a charge of -1 (\(\mathrm{ClO}_{2}^{-}\)). To balance the charges, we need two chlorite ions for every tin ion. Hence, the formula is \(\mathrm{Sn(ClO}_{2})_{2}\).

Write the Formula for Cobalt(II) Hydroxide

Cobalt(II) has a charge of +2 (\(\mathrm{Co}^{2+}\)), and hydroxide has a charge of -1 (\(\mathrm{OH}^{-}\)). Thus, two hydroxide ions are required to balance one cobalt ion's charge. Consequently, the formula is \(\mathrm{Co(OH)_{2}}\).

Write the Formula for Mercurous Phosphate

Mercurous (also referred to as \(\mathrm{Hg}_{2}^{2+}\)) has a charge of +2, shared between two mercury atoms, and phosphate has a -3 charge (\(\mathrm{PO}_{4}^{3-}\)). As a result, three mercurous ions are needed for two phosphate ions to balance the total charges. Therefore, the formula is \(\mathrm{Hg}_{2}_{3}(\mathrm{PO}_{4})_{2}\).

Key concepts

Ternary Compounds

Ternary compounds are intriguing chemical structures that consist of three elements. Usually, these are a metal and a complex ion. Complex ions like sulfate (\(\mathrm{SO}_{4}^{2-}\)), chlorite (\(\mathrm{ClO}_{2}^{-}\)), and phosphate (\(\mathrm{PO}_{4}^{3-}\)) are common in such compounds. These compounds often arise when metal ions bond with these complex ions in a lattice-like structure, creating a more stable entity.

Understanding ternary compounds requires recognizing how these ions fit together to neutralize the compound's charge. For example, a ternary compound formed from lead(IV) and sulfate will include one lead ion with a +4 charge and several sulfate ions with a -2 charge each. The concept of charge balancing is crucial to writing the correct chemical formula for any ternary compound.

When constructing ternary compounds, it's essential to list the metal ion first, followed by the complex ion in parentheses if more than one is needed to balance charges. This order helps us visualize and correctly write the formula.

Ion Charge Balance

Ion charge balance is an essential principle in chemistry that ensures the neutrality of any compound's charge. In ternary compounds, the combination of metal ions and complex ions results in balancing positive and negative charges so that the overall compound is neutral.

To achieve a neutral compound, identify the charges of both the metal ion and the complex ion. The aim is to adjust the number of ions so that the total positive charge equals the total negative charge. For instance, with lead(IV) sulfate, the lead has a charge of +4 and sulfate carries a -2 charge. To balance this, you need two sulfate ions for each lead ion, resulting in the formula \(\mathrm{Pb(SO}_{4})_{2}\).

Always remember: the rules of chemistry dictate that opposite charges attract, and in a neutral compound, these attractions must completely balance out. Using this principle helps derive the correct formulas and understanding how the component ions come together.

Metal Ions

Metal ions are atoms from metallic elements that have lost one or more electrons, resulting in a positively charged ion. They are crucial players in forming both binary and ternary compounds. Metal ions can be found on the left side of the periodic table, typically in groups like the alkali metals, alkaline earth metals, and transition metals.

Each metal ion carries a specific positive charge, often referred to by a Roman numeral in parentheses after the metal name. This denotes the charge, which is crucial for determining the ratios needed to form a neutral compound. For example, in cobalt(II) hydroxide, cobalt bears a +2 charge and pairs with negatively charged ions to form a balanced chemical formula.

When writing formulas, always place the metal ion first, as metals tend to donate electrons, forming bonds with non-metal ions or complex ions to satisfy charge balance. Understanding the specific charge of metal ions in ternary compounds is essential, as it dictates how many complex ions are needed to achieve overall neutrality.

Complex Ions

Complex ions are charged entities composed of several atoms bonded together. They typically include a central atom bonded to surrounding molecules or ions, often having negative charges. Examples include sulfate (\(\mathrm{SO}_{4}^{2-}\)), chlorite (\(\mathrm{ClO}_{2}^{-}\)), and hydroxide (\(\mathrm{OH}^{-}\)).

In ternary compounds, complex ions partner with metal ions to form stable structures. It’s important to note the charge of the complex ion when balancing the formula. For example, in stannous chlorite, the complex ion is chlorite with a -1 charge, requiring two chlorite ions to balance one tin ion of +2 charge, resulting in \(\mathrm{Sn(ClO}_{2})_{2}\).

Complex ions often appear in chemistry as part of polyatomic ions, which means understanding their structure and charge is crucial to mastering compound formation. Each complex ion has specific rules for naming and bonding, which influences how they are used in combination with metal ions to create neutral, reliable compounds.