Question

Name each molecule. \(\begin{array}{ll}{\text { a. SeO }_{2}} & {\text { c. } \mathrm{N}_{2} \mathrm{F}_{4}} \\ {\text { b. SeO }_{3}} & {\text { d. } \mathrm{S}_{4} \mathrm{N}_{4}}\end{array}\)

Short answer

The compound names for the given molecules are as follows: a. SeO₂ - Selenium dioxide b. SeO₃ - Selenium trioxide c. N₂F₄ - Dinitrogen tetrafluoride d. S₄N₄ - Tetrasulfur tetranitride

Step-by-step solution

Name of molecule(a) - SeO2

The compound SeO₂ contains one selenium atom and two oxygen atoms. As it is a covalent compound, we use numerical prefixes to name it. For one selenium atom, we do not use a prefix, and for two oxygen atoms, we use the prefix "di". Thus, the name of SeO₂ is Selenium dioxide.

Name of molecule(b) - SeO3

The compound SeO₃ contains one selenium atom and three oxygen atoms. As it is a covalent compound, we use numerical prefixes to name it. For one selenium atom, we do not use a prefix, and for three oxygen atoms, we use the prefix "tri". Thus, the name of SeO₃ is Selenium trioxide.

Name of molecule(c) - N2F4

The compound N₂F₄ contains two nitrogen atoms and four fluorine atoms. As it is a covalent compound, we use numerical prefixes to name it. For two nitrogen atoms, we use the prefix "di", and for four fluorine atoms, we use the prefix "tetra". Thus, the name of N₂F₄ is Dinitrogen tetrafluoride.

Name of molecule(d) - S4N4

The compound S₄N₄ contains four sulfur atoms and four nitrogen atoms. As it is a covalent compound, we use numerical prefixes to name it. For four sulfur atoms, we use the prefix "tetra", and for four nitrogen atoms, we use the prefix "tetra". Thus, the name of S₄N₄ is Tetrasulfur tetranitride.

Key concepts

Chemical Compound Naming

Understanding how to name chemical compounds is essential for any student of chemistry. This process, known as nomenclature, involves a set of rules and conventions that help scientists communicate unambiguously about chemical substances. In the case of molecular compounds, which are made of nonmetals, we use covalent compound prefixes to indicate the quantity of each atom present in a molecule.

For example, carbon dioxide, a molecule consisting of one carbon atom and two oxygen atoms, is named using the prefix 'di-' to represent the two oxygen atoms. The first element, carbon, keeps its elemental name, while the second element, oxygen, is modified to end with '-ide'. It's important for students to remember that prefixes are used based on the number of atoms, not their atomic weight or other characteristics.

The steps involved in naming SeO2 and SeO3 illustrate this concept clearly. Students should note that while a prefix isn't used for a single atom of the first element, the second element's prefix changes depending on the number of atoms present – 'di-' for two and 'tri-' for three.

Covalent Compound Prefixes

Covalent compound prefixes are integral in identifying the number of atoms of each element in a molecule. When two nonmetal elements form a covalent bond, we determine the amount of each element present and use the appropriate numerical prefixes:

• mono- (1) Not usually used for the first element
• di- (2)
• tri- (3)
• tetra- (4)
• penta- (5)
• hexa- (6)
• hepta- (7)
• octa- (8)
• nona- (9)
• deca- (10)

These prefixes precede the name of each element within the compound. Following our previous examples, N2F4 is named dinitrogen tetrafluoride, showcasing the use of 'di-' for two nitrogen atoms and 'tetra-' for four fluorine atoms. While there are rules and conventions, there are also exceptions, such as omitting the prefix 'mono-' for the first element, as seen with 'carbon monoxide' (CO) instead of 'monocarbon monoxide'.

Molecular Formulas

Molecular formulas provide a straightforward representation of the composition of a compound. They indicate the types of atoms present and the exact number of each atom. In a molecular formula, the chemical symbols for the elements are followed by subscripts showing the number of atoms of each element.

Take, for instance, the molecular formula S4N4, which means a single molecule is composed of four sulfur atoms and four nitrogen atoms. Molecular formulas are not only important for naming chemicals but also for understanding their physical and chemical properties. Being able to discern the information given by a molecular formula is a foundational skill in chemistry, allowing for the interpretation of the compound's structure and reactivity. Students should practice reading and writing molecular formulas to become proficient in their understanding of molecular composition and the consequent naming of compounds.