Question

Write chemical formulas for the following molecular compounds: (a) phosphorus tribromide, (b) dinitrogen tetrafluoride, (c) xenon tetroxide, (d) selenium trioxide.

Short answer

(a) \( \text{PBr}_3 \), (b) \( \text{N}_2\text{F}_4 \), (c) \( \text{XeO}_4 \), (d) \( \text{SeO}_3 \).

Step-by-step solution

Understand Molecular Prefixes

Each prefix in the name of a molecular compound indicates the number of atoms present for that element. For example, 'tri-' indicates three, 'tetra-' indicates four, 'di-' indicates two.

Translate "Phosphorus Tribromide"

The prefix 'tri-' means three, so 'tribromide' indicates there are three bromine atoms. The formula for phosphorus tribromide is \( \text{PBr}_3 \).

Translate "Dinitrogen Tetrafluoride"

The prefix 'di-' means two, and 'tetra-' means four, so 'dinitrogen tetrafluoride' indicates there are two nitrogen atoms and four fluorine atoms. The formula is \( \text{N}_2\text{F}_4 \).

Translate "Xenon Tetroxide"

The prefix 'tetra-' means four, so 'tetroxide' indicates there are four oxygen atoms. The formula for xenon tetroxide is \( \text{XeO}_4 \).

Translate "Selenium Trioxide"

The prefix 'tri-' means three, so 'trioxide' indicates there are three oxygen atoms. The formula for selenium trioxide is \( \text{SeO}_3 \).

Key concepts

Molecular Compounds

Molecular compounds are substances formed when two or more nonmetals chemically bond by sharing electrons. Unlike ionic compounds, which are formed between metals and nonmetals, molecular compounds are held together by covalent bonds. These bonds involve the sharing of electron pairs between atoms, resulting in a more flexible and varied range of structures and properties. Molecular compounds can be simple, with just a couple of atoms, or quite complex. They are typically characterized by low melting and boiling points since the intermolecular forces are generally weaker than those in ionic compounds. Examples include water (H₂O), carbon dioxide (CO₂), and the compounds discussed in this task, such as phosphorus tribromide (PBr₃). Understanding the nature of molecular compounds is essential for grasping how they interact and behave in different chemical environments.

Chemical Nomenclature

Chemical nomenclature is the systematic way in which chemicals are named. In the context of molecular compounds, it involves using a set of rules and conventions established by IUPAC (International Union of Pure and Applied Chemistry) to ensure consistency and clarity. The primary purpose of nomenclature is to provide unambiguous names for chemical substances so that their formulas and structures can be easily understood. This is crucial in scientific communication to avoid misunderstandings. For example, each part of a compound name provides specific information about its structure, such as the type of atoms and their quantities. Therefore, a name like dinitrogen tetrafluoride tells us not only the elements involved—nitrogen and fluorine—but also their stoichiometry: two nitrogen atoms and four fluorine atoms.

Molecular Prefixes

Molecular prefixes are a fundamental part of naming molecular compounds. They offer a quick way to indicate the number of atoms of each element present in a compound. These prefixes are derived from Latin or Greek numbers and are commonly used in the nomenclature of molecular compounds.

• "Mono-" signifies one (often omitted in the first element).
• "Di-" signifies two.
• "Tri-" signifies three.
• "Tetra-" signifies four.
• "Penta-" signifies five, and so on.

For instance, the compound xenon tetroxide uses "tetra-" to indicate four oxygen atoms surrounding one xenon atom. Decoding these prefixes helps in establishing the precise chemical formula from the given name, aiding in both writing and understanding chemical equations efficiently.

Compound Naming

The naming of compounds, particularly molecular compounds, follows a specific set of rules. When naming such a compound, the less electronegative element is usually mentioned first, followed by the more electronegative element, with its name modified to an "-ide" suffix. This systematic approach helps create consistent naming across the board. For example, in the compound phosphorus tribromide, phosphorus is named first because it's less electronegative than bromine. Bromine becomes "bromide" when used in the compound name, indicating its role in the bonding structure. Also, considering molecular prefixes is key in this naming format. The PREFIX-Element1 followed by PREFIX-Element2-IDE structure is often the pattern to watch for. Being familiar with this pattern allows precise identification and the naming of a wide diversity of chemical compounds.