Question

Name the following molecular compounds: (a) \(\mathrm{PCl}_{3}\) (b) \(\mathrm{N}_{2} \mathrm{O}_{3}\) (c) \(\mathrm{P}_{4} \mathrm{O}_{7}\) (d) \(\mathrm{BrF}_{3}\) (e) \(\mathrm{NCl}_{3}\) (f) \(\mathrm{P}_{4} \mathrm{O}_{6}\) (g) \(\mathrm{S}_{2} \mathrm{~F}_{2}\) (h) \(\mathrm{SeO}_{2}\)

Short answer

(a) Phosphorus trichloride (b) Dinitrogen trioxide (c) Tetraphosphorus heptaoxide (d) Bromine trifluoride (e) Nitrogen trichloride (f) Tetraphosphorus hexoxide (g) Disulfur difluoride (h) Selenium dioxide

Step-by-step solution

Understanding Prefixes

In molecular compounds, prefixes are used to denote the number of atoms present. The prefixes are: 1 - mono-, 2 - di-, 3 - tri-, 4 - tetra-, 5 - penta-, 6 - hexa-, 7 - hepta-, 8 - octa-, 9 - nona-, 10 - deca-. These prefixes are added to the name of each element in the compound, indicating the number of times one atom occurs in the compound.

Element Naming Rules

For naming the compound, the element that is more to the left and/or down in the periodic table is named first. The second element is named by taking the root of the element and adding the suffix '-ide'.

Naming \(\mathrm{PCl}_{3}\)

The compound contains phosphorus (P) and chlorine (Cl). Since there is 1 phosphorus atom, the prefix mono- is usually omitted, and for the 3 chlorine atoms, the prefix is tri-. The name is phosphorus trichloride.

Naming \(\mathrm{N}_{2} \mathrm{O}_{3}\)

The compound contains nitrogen (N) and oxygen (O). There are 2 nitrogen atoms (di-) and 3 oxygen atoms (tri-). The name is dinitrogen trioxide.

Naming \(\mathrm{P}_{4} \mathrm{O}_{7}\)

The compound contains phosphorus (P) and oxygen (O). There are 4 phosphorus atoms (tetra-) and 7 oxygen atoms (hepta-). The name is tetraphosphorus heptaoxide.

Naming \(\mathrm{BrF}_{3}\)

The compound contains bromine (Br) and fluorine (F). Since there is 1 bromine atom, the prefix mono- is omitted, and for the 3 fluorine atoms, the prefix is tri-. The name is bromine trifluoride.

Naming \(\mathrm{NCl}_{3}\)

The compound contains nitrogen (N) and chlorine (Cl). Since there is 1 nitrogen atom, the prefix mono- is omitted, and for the 3 chlorine atoms, the prefix is tri-. The name is nitrogen trichloride.

Naming \(\mathrm{P}_{4} \mathrm{O}_{6}\)

The compound contains phosphorus (P) and oxygen (O). There are 4 phosphorus atoms (tetra-) and 6 oxygen atoms (hexa-). The name is tetraphosphorus hexoxide.

Naming \(\mathrm{S}_{2} \mathrm{F}_{2}\)

The compound contains sulfur (S) and fluorine (F). There are 2 sulfur atoms (di-) and 2 fluorine atoms (di-). The name is disulfur difluoride.

Naming \(\mathrm{SeO}_{2}\)

The compound contains selenium (Se) and oxygen (O). Since there is 1 selenium atom, the prefix mono- is omitted, and for the 2 oxygen atoms, the prefix is di-. The name is selenium dioxide.

Key concepts

Chemical Nomenclature

Chemical nomenclature involves the systematic naming of chemical compounds. This enables scientists to communicate clearly and understand the composition of substances easily. For molecular compounds, it entails specific rules that are followed to ensure uniformity across scientific discussions and documentation.

• Elements in a compound are named sequentially based on their position in the periodic table.
• The first element is named fully, while the second element's name is modified by adding the suffix "-ide."

Understanding these guidelines helps avoid confusion, particularly when dealing with compounds comprised of two or more elements. It's crucial to recognize and apply these rules to properly name and understand molecular compounds.

Molecular Compound Prefixes

Molecular compound prefixes illustrate how many atoms of each element are present in the compound. These prefixes, derived from Greek numbers, are critical in correctly naming compounds. They are placed before the element name and are as follows:

• 1 atom - mono- (often omitted for the first element)
• 2 atoms - di-
• 3 atoms - tri-
• 4 atoms - tetra-
• 5 atoms - penta-
• 6 atoms - hexa-
• 7 atoms - hepta-
• 8 atoms - octa-
• 9 atoms - nona-
• 10 atoms - deca-

For example, in the name tetraphosphorus heptaoxide, "tetra-" indicates four phosphorus atoms, while "hepta-" indicates seven oxygen atoms. Mastering these prefixes is essential for accurately conveying the composition of molecular compounds.

Binary Compounds

Binary compounds consist of two different elements. These can be metals combined with nonmetals or, as in the case of molecular compounds, nonmetals with nonmetals. Naming binary compounds involves:

• Identifying the two elements involved.
• Using a prefix to denote the number of each element if necessary.
• Adding a suffix "-ide" to the name of the second element.

For instance, \(Cl_{3}\) in nitrogen trichloride signifies three chlorine atoms, where "tri" stands for three. Understanding the basic structure and naming conventions of binary compounds is a fundamental step in mastering chemical nomenclature.

Chemical Formulas

Chemical formulas are symbolic representations of the composition of chemical compounds. They display the types and numbers of atoms present in molecules using element symbols and numerical subscripts. For molecular compounds, a chemical formula reflects the actual number of atoms of each element in a molecule.

• The first element in the formula often sets the basis for naming.
• Subscripts indicate the number of atoms. For example, \( \mathrm{S}_{2} \mathrm{F}_{2} \) reveals that there are two sulfur and two fluorine atoms in disulfur difluoride.
• Understanding and interpreting chemical formulas allows one to deduce the exact makeup of a compound and aids in accurate naming.

Practicing with chemical formulas enhances one’s ability to visualize and understand chemical compounds, aiding in successfully performing chemical nomenclature.