Problem 77 - Chemistry: The Central Science

Question

Give the name or chemical formula, as appropriate, for each of the following binary molecular substances: (a) \(\mathrm{SF}_{6}\), (b) \(\mathrm{IF}_{5}\), (c) \(\mathrm{XeO}_{3}\), (d) dinitrogen tetroxide, (e) hydrogen cyanide, (f) tetraphosphorus hexasulfide.

Step-by-Step Solution

Answer

a) Sulfur hexafluoride b) Iodine pentafluoride c) Xenon trioxide d) \(\mathrm{N}_{2}\mathrm{O}_{4}\) e) \(\mathrm{HCN}\) f) \(\mathrm{P}_{4}\mathrm{S}_{6}\)

Step 1: Identifying Elements And Prefixes

For the given molecular substances, the required elements and prefixes corresponding to the number of atoms are as follows: a) \(\mathrm{SF}_{6}\): - Sulfur (S): 1 atom (no prefix) - Fluorine (F): 6 atoms (hexa) b) \(\mathrm{IF}_{5}\): - Iodine (I): 1 atom (no prefix) - Fluorine (F): 5 atoms (penta) c) \(\mathrm{XeO}_{3}\): - Xenon (Xe): 1 atom (no prefix) - Oxygen (O): 3 atoms (tri) d) Dinitrogen tetroxide: - Nitrogen (N): 2 atoms (di) - Oxygen (O): 4 atoms (tetra) e) Hydrogen cyanide: - Hydrogen (H): 1 atom (no prefix) - Cyanide (CN): 1 unit (no prefix) f) Tetraphosphorus hexasulfide: - Phosphorus (P): 4 atoms (tetra) - Sulfur (S): 6 atoms (hexa)

Step 2: Determining the Name or Chemical Formula

Now we will determine the name or chemical formula for each of the given molecular substances: a) \(\mathrm{SF}_{6}\): - One sulfur atom, six fluorine atoms - Name: Sulfur hexafluoride b) \(\mathrm{IF}_{5}\): - One iodine atom, five fluorine atoms - Name: Iodine pentafluoride c) \(\mathrm{XeO}_{3}\): - One xenon atom, three oxygen atoms - Name: Xenon trioxide d) Dinitrogen tetroxide: - Chemical formula: \(\mathrm{N}_{2}\mathrm{O}_{4}\) e) Hydrogen cyanide: - Chemical formula: \(\mathrm{HCN}\) f) Tetraphosphorus hexasulfide: - Chemical formula: \(\mathrm{P}_{4}\mathrm{S}_{6}\)

Key Concepts

Chemical Nomenclature

Chemical nomenclature is the system used to name chemical substances so that they can be easily identified and distinguished from one another. Binary molecular compounds consist of two non-metal elements. Naming these compounds involves specific rules, depending on the elements involved and their quantities.

• Element Order: The element that is less electronegative is usually written first in the name and formula.
• Element Naming: The name of the first element remains unchanged, while the second element's name is altered to end with "-ide."
• Prefixes Usage: Prefixes are essential in naming to indicate the number of atoms of each element present. However, the prefix "mono-" is generally omitted for the first element.

Through these rules, compounds such as sulfur hexafluoride (\( \mathrm{SF}_6 \)) can be consistently named, ensuring universal understanding across scientific communities. By understanding this system, students can decipher and construct names for given chemical formulas like iodine pentafluoride or generate formulas for names like dinitrogen tetroxide.

Molecular Formulas

Molecular formulas are compact representations of the types and numbers of atoms in a molecule. The formula lists elements, with subscripts indicating how many atoms of each element are present. For example, the molecular formula \(\mathrm{SF}_6\) shows there is one sulfur atom and six fluorine atoms.

• Understanding Subscripts: The subscript numbers inform us about the precise quantity of each element present in one molecule, which is critical for chemical reactions and understanding a compound's properties.
• No Subscript Implies One: If an element symbol in the formula does not have a subscript, it is understood that only one atom of that element is present.

Keeping these simple yet powerful patterns in mind helps in transforming names like xenon trioxide to its chemical formula \(\mathrm{XeO}_3\) or conversely determining that a formula like \(\mathrm{P}_4\mathrm{S}_6\) represents tetraphosphorus hexasulfide.

Chemical Prefixes

Chemical prefixes are fundamental in naming binary molecular compounds. They provide clear information on the number of atoms of each element present in the compound. These prefixes are usually derived from Greek and are used consistently to avoid confusion.

• Common Prefixes: Some prefixes include "mono-" (1), "di-" (2), "tri-" (3), "tetra-" (4), "penta-" (5), "hexa-" (6), and so forth.
• Application in Naming: These prefixes precede the element name to convey the number of atoms, such as "tetra" for four (as seen in tetraphosphorus) or "hexa" for six (as seen in hexafluoride).
• Exceptions in Usage: The "mono-" prefix is often skipped when naming the first element, so carbon monoxide is an exception where "mono-" is used with the second element.

Mastering these prefixes and their correct usage makes it much easier to interpret both the names and formulas of compounds such as dinitrogen tetroxide (\( \mathrm{N}_2\mathrm{O}_4 \)) or hydrogen cyanide (\( \mathrm{HCN} \)).