Part 1 - Naming Ionic and Polyatomic Compounds

Writing Names and Formulas for Ionic Compounds

• Audience: SCH 3U students

Reflection

• Quote by J.K. Rowling: “Call him Voldemort, Harry. Always use the proper name for things. Fear of a name increases fear of the thing itself.”

  • Signifies the importance of proper naming in chemistry.

Learning Goals

• Be able to:

  • Write the name and formula of ionic compounds (binary, polyatomic, multivalent)

  • Write the name and formula for molecular compounds

  • Write the name and formula for hydrates

  • Write the name and formula for acids

Importance of Naming

• Example Showing Importance:

  • Different names for the same compound, Calcium carbonate

  • Names include: Kreda, Craie, Sialc, Gesso, Tiza, Krijt (all refer to chalk, CaCO3).

IUPAC

• Definition: International Union for Pure and Applied Chemistry (1919)

  • Purpose: Standardize names for chemical compounds.

• Importance:

  • Ensures safety

  • Aids in research

  • Facilitates patenting processes

Naming Binary Ionic Compounds

• Example: Na2O

  • Step 1: Name the metal ion first; followed by the non-metal ion.

  • Step 2: The name of the metal ion (cation) is the same as its atom name.

    • E.g., Sodium (Na) for sodium ion, Oxygen (O) for non-metal.

  • Step 3: Transition metals may require roman numerals for charge specification.

    • E.g., Iron (III) for Fe3+; Iron (II) for Fe2+.

  • Sodium charge: +1; no roman numeral needed.

Naming Multivalent Ions

• Differentiate charges using suffixes:

  • Lower charge: -ous

  • Higher charge: -ic

• Examples:

  • Iron (II) is ferrous; Iron (III) is ferric.

  • Gold (I) is aurous; Gold (III) is auric.

  • Copper (I) is cuprous; Copper (II) is cupric.

  • Tin (II) is stannous; Tin (IV) is stannic.

  • Lead (II) is plumbous; Lead (IV) is plumbic.

  • Mercury (I) is mercurous; Mercury (II) is mercuric.

Naming Binary Ionic Compounds in Summary

• Steps to Name:

  1. Name the metal ion first.

  2. Cation's name is the same as the metal atom's name.

  3. Use roman numerals if the metal cation has more than one charge.

  4. Name the non-metal ion with root name + -ide suffix.

  • Example: Na2O is sodium oxide.

Polyatomic Ions (Oxyanions)

• Contain positive cation and polyatomic anion.

• Typical ending: -ate. Examples include:

  • Pattern: [XO3]-.

  • Important exceptions: CO32- (carbonate), SO42- (sulfate), PO43- (phosphate).

Variations with Polyatomic Ions

• Alternate forms exist based on oxygen count:

• Example: Chlorate variations:

  • Hypochlorite (ClO-)

  • Chlorite (ClO2-)

  • Chlorate (ClO3-)

  • Perchlorate (ClO4-)

Rules for Naming Ionic Compounds with Polyatomic Ions

• Similar to binary compounds but without adding -ide.

• Example: Iron (III) carbonate.

Common Polyatomic Ions Table (Table 2.4)

• List of common names and formulas:

• Ammonium (NH₄+)

• Nitrate (NO3-)

• Acetate (C2H3O2-)

• Sulfate (SO4^2-)

• Phosphate (PO4^3-), etc.

Steps for Naming Ionic Compounds using Polyatomic Ions

1. Identify cation and anion

   • Example: Iron (Fe) is cation, Carbonate (CO3) is anion.

2. Get chemical symbols from periodic table or polyatomic table.

3. Determine ionic charges from tables.

4. Ensure charges balance (net charge = 0).

   • Example: If Fe is +3 and CO3 is -2, cross to create Fe2(CO3)3.

Writing Formulas for Ionic Compounds

• Example: Copper (II) nitrate

  • Step 1: Identify ions: Copper (II) + Nitrate (NO3-).

  • Step 2: Write symbols (Cu2+, NO3-).

  • Step 3: Assign superscripts for charges. Copper (II) = 2+, Nitrate = -1.

  • Step 4: Balance charges: Cu(NO3)2, needs two nitrate for one copper.

Criss-Cross Rule

• Use superscripts of one ion as subscripts for the other ion, excluding the charge.

Homework

• Complete worksheets on Naming and Writing Formulas for Ionic Compounds and the Crossover Rule.