Chemistry 9

3. Naming Compounds

1. Naming Ionic Compounds

Ionic compounds are formed between metals and nonmetals.

Binary Ionic Compounds (Two Elements)

1. Name the Metal First: Use its full name.
2. Name the Nonmetal Second: Change its ending to "-ide."

Example:

Transition Metals with Variable Charges

1. Use Roman numerals to indicate the metal's charge.
2. Name the nonmetal with the "-ide" ending.

Example:

2. Naming Covalent (Molecular) Compounds

Covalent compounds are formed between two nonmetals.

1. Use prefixes to indicate the number of atoms in each element.
2. The second element's name ends with "-ide."
3. Omit the prefix "mono-" for the first element if there’s only one atom.

Prefixes:

• 1: Mono-
• 2: Di-
• 3: Tri-
• 4: Tetra-
• 5: Penta-
• 6: Hexa-
• 7: Hepta-
• 8: Octa-
• 9: Nona-
• 10: Deca-

Example:

3. Naming Polyatomic Ionic Compounds

Compounds containing polyatomic ions (groups of atoms with a charge) require the names of the ions.

1. Name the metal first.
2. Name the polyatomic ion without changing its name.

Common Polyatomic Ions:

• $\text{NO}_3^-$NO3−​: Nitrate
• $\text{SO}_4^{2-}$SO42−​: Sulfate
• $\text{CO}_3^{2-}$CO32−​: Carbonate
• $\text{OH}^-$OH−: Hydroxide
• $\text{NH}_4^+$NH4+​: Ammonium
• $\text{PO}_4^{3-}$PO43−​: Phosphate

Example:

4. Naming Acids

Acids are compounds that release hydrogen ions ($\text{H}^+$H+) in solution.

Binary Acids (No Oxygen)

1. Use the prefix "hydro-" for the nonmetal.
2. Add the suffix "-ic acid."

Example:

Oxyacids (Contain Oxygen)

1. Do not use "hydro-" in the name.
2. Replace "-ate" in the polyatomic ion with "-ic acid."
3. Replace "-ite" in the polyatomic ion with "-ous acid."

Example:

5. Writing Formulas from Names

1. Determine the Elements and Charges: Identify the symbols and charges of the ions or elements.
2. Balance the Charges: Use subscripts to balance the total positive and negative charges.

Example:

6. Recognizing Special Cases

1. Hydrates: Compounds that include water molecules.

   • Use prefixes to indicate the number of water molecules.
   • Example: $\text{CuSO}_4 \cdot 5\text{H}_2\text{O} \rightarrow \text{Copper(II) sulfate pentahydrate}$CuSO4​⋅5H2​O→Copper(II) sulfate pentahydrate.

2. Peroxides and Superoxides: Include the term "peroxide" or "superoxide" for compounds like $\text{H}_2\text{O}_2$H2​O2​ (hydrogen peroxide).

7. Practice with Real-Life Examples

• Table Salt: $\text{NaCl}$NaCl → Sodium chloride
• Baking Soda: $\text{NaHCO}_3$NaHCO3​ → Sodium bicarbonate
• Water: $\text{H}_2\text{O}$H2​O → Dihydrogen monoxide (or simply water)

Activities for Mastery

1. Flashcards: Practice common ions and their charges.
2. Naming Games: Match formulas to names and vice versa.
3. Hands-On Labs: Use real compounds (e.g., vinegar, baking soda) and identify their names and formulas.

By focusing on these essentials, Grade 9 students will develop a strong foundation in naming compounds and applying these principles in chemistry.