Question

In the following pairs of binary compounds determine which one is a molecular substance and which one is an ionic substance. Use the appropriatenaming convention (for ionic or molecular substances) to assign a name to each compound: (a) \(\mathrm{SiF}_{4}\) and \(\mathrm{LaF}_{3}\), (b) \(\mathrm{FeCl}_{2}\) and \(\mathrm{ReCl}_{6}\), (c) \(\mathrm{PbCl}_{4}\) and \(\mathrm{RbCl}\)

Short answer

In the given pairs of compounds: (a) \(\mathrm{SiF}_{4}\) is a molecular compound named Silicon tetrafluoride, and \(\mathrm{LaF}_{3}\) is an ionic compound named Lanthanum fluoride. (b) \(\mathrm{FeCl}_{2}\) is an ionic compound named Iron(II) chloride, and \(\mathrm{ReCl}_{6}\) is an ionic compound named Rhenium(VI) chloride. (c) \(\mathrm{PbCl}_{4}\) is an ionic compound named Lead(IV) chloride, and \(\mathrm{RbCl}\) is an ionic compound named Rubidium chloride.

Step-by-step solution

Identify the Type of Bonding

To determine whether a compound is molecular or ionic, we can look at the elements involved. If the compound consists of a metal and a non-metal, it is most likely an ionic compound. If the compound consists of only non-metal elements, it is likely a molecular compound. Using this, we can classify each compound as follows: (a) \(\mathrm{SiF}_{4}\): Si is a metalloid and F is a non-metal, so this compound is molecular. \(\mathrm{LaF}_{3}\): La is a metal and F is a non-metal, so this compound is ionic. (b) \(\mathrm{FeCl}_{2}\): Fe is a metal and Cl is a non-metal, so this compound is ionic. \(\mathrm{ReCl}_{6}\): Re is a metal and Cl is a non-metal, so this compound is ionic. (c) \(\mathrm{PbCl}_{4}\): Pb is a metal and Cl is a non-metal, so this compound is ionic. \(\mathrm{RbCl}\): Rb is a metal and Cl is a non-metal, so this compound is ionic.

Name Each Compound Using the Appropriate Naming Convention

Now that we've identified whether each compound is molecular or ionic, we can name them using the appropriate naming conventions: (a) \(\mathrm{SiF}_{4}\): This is a molecular compound, so we use prefixes to indicate the number of atoms. The name is Silicon tetrafluoride. \(\mathrm{LaF}_{3}\): This is an ionic compound, so we use the names of the metal and non-metal. The name is Lanthanum fluoride. (b) \(\mathrm{FeCl}_{2}\): This is an ionic compound, so we use the names of the metal and non-metal. Since Fe can have multiple charges, we need to indicate its charge in the name. In this case, there are two Cl atoms, so Fe must have a charge of +2. The name is Iron(II) chloride. \(\mathrm{ReCl}_{6}\): This is an ionic compound, so we use the names of the metal and non-metal. Since Re can have multiple charges, we need to indicate its charge in the name. In this case, there are six Cl atoms, so Re must have a charge of +6. The name is Rhenium(VI) chloride. (c) \(\mathrm{PbCl}_{4}\): This is an ionic compound, so we use the names of the metal and non-metal. Since Pb can have multiple charges, we need to indicate its charge in the name. In this case, there are four Cl atoms, so Pb must have a charge of +4. The name is Lead(IV) chloride. \(\mathrm{RbCl}\): This is an ionic compound, so we use the names of the metal and non-metal. The name is Rubidium chloride.

Key concepts

Ionic Compounds

Ionic compounds are made up of charged particles known as ions. Usually, they consist of metals and non-metals. These types of compounds form when one atom donates an electron to another atom.

• Metals, which are found on the left side of the periodic table, typically lose electrons to form positive ions or cations.
• Non-metals, found on the right side of the periodic table, typically gain electrons to form negative ions or anions.

An example of an ionic compound is LaF\(_3\), Lanthanum fluoride. Here, Lanthanum (La) is a metal and donates electrons to Fluorine (F), a non-metal. This incompatibility results in a strong attraction between the oppositely charged ions.Understanding the formation of ionic compounds can help with the naming and recognizing of the compound types in chemical nomenclature.

Molecular Compounds

Molecular compounds are also known as covalent compounds. They are primarily formed when non-metal atoms share electrons, instead of donating them like in ionic compounds. Here, elements are bonded by covalent bonds.

• This type of bonding happens between two or more non-metals.
• Atoms achieve stable electron configurations by sharing electrons.

For instance, in SiF\(_4\) (Silicon tetrafluoride), silicon and fluorine are both non-metals. They come together by sharing electrons to form a stable compound. Compared to ionic bonds, molecular compounds usually have lower melting points and are poor conductors of electricity. These traits are essential when categorizing substances as molecular in chemical nomenclature.

Bonding Types

Understanding bonding types is crucial for identifying chemical substances.

• Ionic Bonding: This involves the transfer of electrons from metals to non-metals and forming ionic compounds like LaF\(_3\) (Lanthanum fluoride).
• Covalent Bonding: Predominantly occurs between non-metal atoms which share electrons, resulting in molecular compounds, such as SiF\(_4\) (Silicon tetrafluoride).
• Metallic Bonding: Involves the bonding of metal atoms, where electrons flow freely among a lattice of atoms.

These types of bonding not only affect the properties of a compound but also guide the way compounds are named in chemical nomenclature. Recognizing which type of bonding is present helps simplify the identification process.

Naming Conventions

Chemical nomenclature is a systematic method of naming chemical compounds. It follows specific conventions to ensure consistency and understanding across different regions and languages.

• Ionic Compounds: Generally named by stating the cation first and the anion second. For example, for LaF\(_3\), the name is Lanthanum fluoride.
• Molecular Compounds: Prefixes indicate the number of each atom. SiF\(_4\) is named as Silicon tetrafluoride, where 'tetra-' means four.
• Compounds with metals that can have multiple charges include a Roman numeral to specify the charge. For instance, FeCl\(_2\) is named Iron(II) chloride to indicate iron's charge.

By understanding naming conventions, students can accurately identify and communicate chemical formulas, enabling a clearer comprehension of chemistry principles.