Question

Name each molecular compound. (a) \(\mathrm{XeF}_{4}\) (b) \(\mathrm{PI}_{3}\) (c) \(\mathrm{SO}_{3}\) (d) \(\mathrm{SiCl}_{4}\) (e) \(\mathrm{I}_{2} \mathrm{O}_{5}\)

Short answer

The names of the compounds are: (a) xenon tetrafluoride, (b) phosphorus triiodide, (c) sulfur trioxide, (d) silicon tetrachloride, (e) diiodine pentoxide.

Step-by-step solution

Naming Molecular Compounds

When naming molecular compounds, the first element is named first using its elemental name. For the second element, its base name is used with an -ide suffix.

Using Greek Prefixes

Greek prefixes are used to denote the number of atoms of each element in the compound (mono- is usually omitted for the first element).

Naming XeF4

For the compound \(\mathrm{XeF}_{4}\), the name is xenon tetrafluoride. Xenon is the first element; tetra- is the Greek prefix for four.

Naming PI3

For the compound \(\mathrm{PI}_{3}\), the name is phosphorus triiodide. Phosphorus is the first element; tri- is the Greek prefix for three.

Naming SO3

For the compound \(\mathrm{SO}_{3}\), the name is sulfur trioxide. Sulfur is the first element; tri- is the Greek prefix for three.

Naming SiCl4

For the compound \(\mathrm{SiCl}_{4}\), the name is silicon tetrachloride. Silicon is the first element; tetra- is the Greek prefix for four.

Naming I2O5

For the compound \(\mathrm{I}_{2}\mathrm{O}_{5}\), the name is diiodine pentoxide. Di- is the Greek prefix for two, and penta- is the Greek prefix for five.

Key concepts

Greek prefixes in chemistry

When studying chemistry, one key aspect students must master is the use of Greek prefixes to name molecular compounds. These prefixes are essential for conveying the number of atoms of each element present in a compound. For instance, the prefix 'mono-' indicates one atom, 'di-' denotes two, and 'tri-' stands for three. However, 'mono-' is commonly omitted when it applies to the first element in a compound.
For example, in the compound carbon dioxide, 'di-' signifies that there are two oxygen atoms. As students progress to compounds with more atoms, they will encounter prefixes such as 'tetra-' for four, 'penta-' for five, 'hexa-' for six, and so on, upto 'deca-' for ten. These prefixes not only help in naming the compounds correctly but also in visualizing their molecular structure, which is a vital part of learning chemistry.

Chemical nomenclature

Chemical nomenclature is the systematic way of naming chemical substances. Each name provides information about the composition and structure of the compound, making it easier to predict how the compound will react with others. In the realm of molecular compounds, names are crafted by combining the name of the first element with a modified version of the name of the second element, usually ending in '-ide'.
For learners encountering this initially, understanding and applying the logic behind these names is crucial. Taking the name 'sulfur hexafluoride' as an example, we can deduce that sulfur is the first element and that there are six (indicated by 'hexa-') fluoride groups attached to it. Consistency in chemical nomenclature allows chemists around the world to communicate unambiguously about compounds and their reactions.

Molecular compound notation

The notation of molecular compounds, often simply termed as chemical formulas, is a concise way to represent the elements and the number of atoms of each present in the compound. It serves as a shorthand that encapsulates the compound's composition, which can be deciphered using the rules of chemical nomenclature.
Students learn to read formulas such as \(\mathrm{NH}_3\) as ammonia, knowing it consists of one nitrogen (N) and three hydrogen (H) atoms. Similarly, \(CO_2\) denotes carbon dioxide, indicating one carbon atom double-bonded to two oxygen atoms. These formulas are not random; they are based on established systematic rules, reflecting the compound's molecular structure. Comprehending these notations is fundamental to understanding the makeup and potential interactions of various molecular compounds in chemistry.