Ionic Compounds Naming and Formulas

Ionic Compounds in the Lab

• Ionic compounds are commonly encountered in the lab.
• They are typically easily handled solids.
• They are usually soluble in water.
• Properly working with these compounds requires knowing how to name them.

Composition and Formula

• Ionic compounds consist of oppositely charged ions held together by electrostatic attractions.
• The formula for an ionic compound lists the positive ion (cation) first, followed by the negative ion (anion).
• Example: NaCl (Sodium Chloride), composed of $Na^+$ and $Cl^-$.

Determining Ion Charges

• The position of an element on the periodic table can often determine the charge(s) of the ion it forms.
• Ions combine in ratios to create a neutral formula unit.

Naming Binary Ionic Compounds

• The name of an ionic compound follows the same order as the formula (cation then anion).
• Binary ionic compounds are the simplest type, composed of only one element per ion.
• Generally, the cation is a metal ion, and the anion is a nonmetal ion.

Naming Convention

• Name the element making up the cation as is.
• Name the element making up the anion, changing the ending to "ide".

Examples

• NaCl: Sodium Chloride (Chlorine becomes Chloride).
• $CaCl_2$: Calcium Chloride (Chlorine becomes Chloride).
• CsBr: Cesium Bromide (Bromine becomes Bromide).
• $Na_2O$: Sodium Oxide (Oxygen becomes Oxide).
• Note: No charges are explicitly stated in the names.
• Compounds are electrically neutral.

Complications with Transition Metals

• Some transition metals can form ions with multiple charges.
• Example: Iron (Fe) can form both $Fe^{2+}$ and $Fe^{3+}$ ions.
• Since these ions are chemically different, the name must indicate the cation's charge.
• This is done by adding the charge as a Roman numeral in parentheses after the cation name.

Determining Charge from Formula

• Determine the charge of the transition metal based on the compound's formula.
• Identify the charge of the anion(s).
• Calculate the charge on the transition metal cation needed for the ratio to give a neutral formula unit.

Examples

• $FeBr_3$: Three Bromide ions (each -1 charge) means Iron ion must be +3. Name is Iron (III) Bromide.
• $TiCl_4$: Four Chloride ions (each -1 charge) means Titanium ion must be +4. Name is Titanium (IV) Chloride.
• $MnF_2$: Two Fluoride ions (each -1 charge) means Manganese ion must be +2. Name is Manganese (II) Fluoride.

Additional Notes

• Familiarize yourself with the charges of common anions.
• Use the periodic table to determine charges for other elements.
• Learn which transition metals do not have multiple oxidation states.
• Practice is key to becoming proficient at naming ionic compounds.