Question

Simple Lewis Structures, Formulas, and Names fo Name each molecular compound. $$ \text { a. }\mathrm{SO}_{3} \quad \text { b. } \mathrm{SO}_{2} \quad \text { c. }\mathrm{BrF}_{5} \quad \text { d. } \mathrm{NO} $$

Short answer

a. Sulfur trioxide b. Sulfur dioxide c. Bromine pentafluoride d. Nitrogen monoxide

Step-by-step solution

Name SO3

Identify the elements sulfur (S) and oxygen (O). The compound is composed of one sulfur atom and three oxygen atoms. Since the compound consists of nonmetals only, it is named by using prefixes to denote the number of each atom. 'Mono-' is usually omitted for the first element. Therefore, SO3 is named sulfur trioxide.

Name SO2

Identify the elements sulfur (S) and oxygen (O). This compound is composed of one sulfur atom and two oxygen atoms. Following the same rule of using prefixes for nonmetals, and omitting 'mono-' for the first element, SO2 is named sulfur dioxide.

Name BrF5

Identify the elements bromine (Br) and fluorine (F). BrF5 consists of one bromine atom and five fluorine atoms. Using prefixes, and again omitting 'mono-' for the first element, BrF5 is named bromine pentafluoride.

Name NO

Identify the elements nitrogen (N) and oxygen (O). The compound consists of one nitrogen atom and one oxygen atom. Since there is only one oxygen atom, the prefix 'mono-' is used before the name of the second element. Therefore, NO is named nitrogen monoxide.

Key concepts

Chemical Nomenclature

The process of naming chemical compounds is known as chemical nomenclature. It's a standardized system that allows chemists to communicate clearly about molecular entities. In the naming of molecular compounds, which are combinations of nonmetals, specific rules are applied to create a standardized name that can be universally understood.

For compounds like sulfur trioxide (SO₃) and nitrogen monoxide (NO), we use a set of naming conventions to ensure that anyone, anywhere, can understand exactly what compound is being referred to. The nomenclature system avoids ambiguity and ensures clarity, which is essential in scientific communication. Each name provides insight not only into which elements are present but also in what quantity.

Chemistry Prefixes

Within chemical nomenclature, chemistry prefixes are critical components. They denote the quantity of each element within a compound. These prefixes are derived from Greek or Latin numbers. For example:

• mono- (1)
• di- (2)
• tri- (3)
• tetra- (4)
• penta- (5)
• hexa- (6)

The prefix 'mono-' is typically omitted for the first element in a compound, as seen in sulfur dioxide (SO₂), not 'monosulfur dioxide'. However, it is used when the compound has just one atom of the second element, like in nitrogen monoxide (NO). By mastering these prefixes, students can name and understand the composition of virtually any molecular compound.

Lewis Structures

Lewis structures, also known as Lewis dot diagrams, are visual representations of the bonding between atoms within a molecule and the lone pair electrons in the molecule. They're named after Gilbert N. Lewis, who introduced them in 1916.

Creating a Lewis structure involves arranging dots around element symbols to represent electrons and using lines to depict covalent bonds. For example, the Lewis structure of NO would show a pair of electrons shared between the nitrogen and oxygen atoms, and additional electron pairs that are not shared. These diagrams are foundational in understanding molecular shape, bond formation, and reactivity.

Molecular Formulas

Molecular formulas provide a concise way of expressing information about the atoms that constitute a particular chemical compound. They illustrate the type of atoms present in the compound as well as the exact number of each atom. For example, BrF₅ indicates the presence of one bromine atom (Br) and five fluorine atoms (F), hence it's called bromine pentafluoride.

Molecular formulas are distinct from structural formulas which display the arrangement of atoms within the molecule. The molecular formula is just one piece of the puzzle but is essential for basic understanding of the compound's composition. It's the first step in analyzing the substance's structure and properties.