Question

Name each molecule. a. \(\mathrm{PCl}_{3}\) b. \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) c. \(\mathrm{P}_{4} \mathrm{O}_{6}\) d. \(\mathrm{NO}\)

Short answer

a. \(\mathrm{PCl}_{3}\): Phosphorus trichloride b. \(\mathrm{Cl}_{2} \mathrm{O}_{7}\): Dichlorine heptoxide c. \(\mathrm{P}_{4} \mathrm{O}_{6}\): Tetraphosphorus hexoxide d. \(\mathrm{NO}\): Nitrogen monoxide

Step-by-step solution

Identify each element in the compound

For each molecule, identify the elements present and recall their names. Pay close attention to the element's position in the periodic table to confirm if they are nonmetals, which typically form covalent compounds. a. \(\mathrm{PCl}_{3}\): Phosphorus (P) and Chlorine (Cl) b. \(\mathrm{Cl}_{2} \mathrm{O}_{7}\): Chlorine (Cl) and Oxygen (O) c. \(\mathrm{P}_{4} \mathrm{O}_{6}\): Phosphorus (P) and Oxygen (O) d. \(\mathrm{NO}\): Nitrogen (N) and Oxygen (O)

Utilize the Greek numerical prefixes

For each molecule, apply the Greek numerical prefixes to indicate the number of atoms of each element in the molecule name. Note that mono- is typically omitted when naming the first element. 1. mono- (1) 2. di- (2) 3. tri- (3) 4. tetra- (4) 5. penta- (5) 6. hexa- (6) 7. hepta- (7) 8. octa- (8) 9. nona- (9) 10. deca- (10)

Name the molecules, considering the above rules

Now that we have the correct naming prefixes, assign the names to each given molecule. a. \(\mathrm{PCl}_{3}\): Phosphorus trichloride b. \(\mathrm{Cl}_{2} \mathrm{O}_{7}\): Dichlorine heptoxide c. \(\mathrm{P}_{4} \mathrm{O}_{6}\): Tetraphosphorus hexoxide d. \(\mathrm{NO}\): Nitrogen monoxide

Conclusion

The given molecules have been correctly named according to the rules for naming covalent compounds: a. \(\mathrm{PCl}_{3}\): Phosphorus trichloride b. \(\mathrm{Cl}_{2} \mathrm{O}_{7}\): Dichlorine heptoxide c. \(\mathrm{P}_{4} \mathrm{O}_{6}\): Tetraphosphorus hexoxide d. \(\mathrm{NO}\): Nitrogen monoxide

Key concepts

Covalent Compounds

Covalent compounds are chemical substances formed by the sharing of electron pairs between atoms. This occurs primarily between nonmetals, which tend to have similar electronegativity values, allowing them to covalently bond rather than transfer electrons. In a covalent bond, each atom contributes at least one electron to form an electron pair shared between the atoms.

These compounds often consist of molecules, which represent the smallest unit of the compound with characteristic properties. For example, water (H₂O) is a well-known covalent compound where two hydrogen atoms share electrons with one oxygen atom. The sharing nature of covalent bonds is what gives these compounds distinctive properties, such as lower melting and boiling points compared to ionic compounds. Covalent compounds can also exist as gases, liquids, or solids at room temperature.

In the context of our problem, molecules like \(\mathrm{PCl}_3\), \(\mathrm{Cl}_2 \mathrm{O}_7\), \(\mathrm{P}_4 \mathrm{O}_6\), and \(\mathrm{NO}\) are examples of covalent compounds. This is because they are composed of nonmetal elements that share electrons to form stable structures.

Greek Numerical Prefixes

Greek numerical prefixes are essential when naming covalent compounds because they indicate the number of atoms of each element present in the molecule.

These prefixes are derived from the Greek language, making them both intuitive and descriptive. They ensure that each molecular compound name conveys precise information about the molecule's structure and composition.

• Mono- (1), often omitted for the first element
• Di- (2)
• Tri- (3)
• Tetra- (4)
• Penta- (5)
• Hexa- (6)
• Hepta- (7)
• Octa- (8)
• Nona- (9)
• Deca- (10)

The application of these prefixes helps in maintaining uniformity and clarity in chemical nomenclature.

For example, in the compound \(\mathrm{PCl}_3\), "tri-" indicates that there are three chlorine atoms bonded to one phosphorus atom.

Molecular Naming Rules

The process of naming covalent compounds follows specific rules to ensure that each name accurately represents the compound's chemical structure. Understanding these rules is crucial for anyone studying chemistry, as they form the foundation for effective communication of chemical information.

1. **Identifying the elements**: Always begin by identifying the elements present in the compound. Recognize that covalent compounds consist largely of nonmetal elements.

2. **Applying prefixes**: Use Greek prefixes to indicate the number of atoms. For the first element in the compound, the prefix "mono-" is usually omitted. The second element often ends with the suffix "-ide."

3. **Ordering elements**: The element further left on the periodic table usually comes first, and the more electronegative element is typically placed at the end.

• For instance, in \(\mathrm{NO}\), nitrogen is named first, followed by oxygen with the suffix, thus creating the name "nitrogen monoxide."
• In \(\mathrm{P}_4 \mathrm{O}_6\), the sequence becomes "tetraphosphorus hexoxide."

These steps ensure clarity and accuracy while providing a descriptive name for each covalent compound.