2B - Ionic Compounds

2b - Naming Ionic Compounds & Formulas

By Marissa Brown

Ionic Bonds

• Occurs between a metal and a non-metal

• Called an ionic bond because the atoms become ions by transferring their electrons

• One gives its electrons up (cation), the other one takes them (anion)

A. Oxidation Numbers

The charge of an ion can be determined by its place on the Periodic Table.

Multiple Choice

Which element has a +2 charge?

• sodium

• magnesium

• potassium

• aluminum

Multiple Choice

What type of element forms an anion (negative ion)?

• metal

• metalloid

• non-metal

Rules for Naming Cations

• When metals lose electrons they become ions, but their name does not change.

Rules for Naming Anions

• When nonmetals gain electrons they become ions, and their name does change.

Rules of Naming Ions

• The names of metals do not change.

• Changing the name of nonmetals:

• root of element name + -ide  = name of anion

• Examples:

  The name of chlorine’s ion: chlor-  +  -ide  =  chloride

• The name of calcium’s ion: calcium

  (The names of metals don’t change!)

• The name of nitrogen’s ion: nitr-  +  -ide  =  nitride

Steps for Naming Ionic Compounds

Step 1: Write the name of the metal ion.

Step 2: Write the name of the nonmetal ion.



Step 3: YOU ARE DONE! It is that easy.

Example: CaBr₂

_{Calcium Bromide}

Naming transition metals

• The names of transition metals include their charge because their charges are less predictable.

• We know they are positive because metals are always positive.

• Examples:

• Copper (I) = Cu⁺

• Iron (II) = Fe²⁺

• Lead (IV) = Pb⁴⁺

Naming with transition metals

• We can determine the charge of the metal from the chemical formula of the compound.

• The sum of all the charges must be zero. 

• What is the charge of iron in FeCl₃?

• Chloride has a charge of -1

• There are 3 chlorides in the compound and only 1 iron

• To have the charge add up to zero the charge of Iron has to be +3

• Name of the compound: Iron (III) Chloride

Writing Ionic Compounds

You can also determine the formula of an ionic compound from its name.

Step 1: Write the symbol of the metal ion.

Step 2: Write the symbol of the nonmetal ion.

Step 3: Determine the charges using the periodic table.

Step 4: Determine the formula from the ions.

Multiple Choice

What is the correct formula for the compound: sodium chloride

• NaCl

• Na₂Cl

• Na₂Cl₂

Multiple Choice

What is the correct formula for the compound: strontium nitride

• Sr₂N₃

• SrN

• Sr₃N₂

The charges of transition metals are important when writing the formula of an ionic compound.

Step 1: Write the symbol of the cation (+)

Step 2: Write the symbol of the anion (-)

Step 3: Determine the charges using the periodic table and the roman numerals.

Step 4: Determine the formula from the ions.

Multiple Choice

What is the correct formula for the compound: copper (I) oxide

• CuO

• CuO₂

• Cu₂O

Multiple Choice

What is the correct formula for the compound: lead (IV) oxide

(Remember to reduce)

• PbO

• Pb₂O₄

• PbO₂

• Pb_2O