Notes: Writing Formulas & Naming Ionic Compounds

Ionic Compounds ions - atoms that have a positive or negative charge ions - atoms that have a positive or negative charge Oxidation number – the charge that an ion has from the gain or los of electrons Oxidation number – the charge that an ion has from the gain or los of electrons

Ionic Compounds Metallic elements tend to form ions by losing one or more electrons, giving them an overall positive charge. These are called cations. Metallic elements tend to form ions by losing one or more electrons, giving them an overall positive charge. These are called cations.

Ionic Compounds Nonmetals tend to form ions by gaining one or more electrons, giving them an overall negative charge. These are called anions. Nonmetals tend to form ions by gaining one or more electrons, giving them an overall negative charge. These are called anions.

Ionic Compounds An ionic compound is formed of cations and anions, this means they are made from a metal and a nonmetal. An ionic compound is formed of cations and anions, this means they are made from a metal and a nonmetal.

Ionic Compounds Anions and cations can also sometimes be made of groups of elements that carry an overall charge called polyatomic ions. Anions and cations can also sometimes be made of groups of elements that carry an overall charge called polyatomic ions.

Ionic Compounds Though made from positively and negatively charged ions, an ionic compound is electrically neutral. Though made from positively and negatively charged ions, an ionic compound is electrically neutral. The total charge of all the ions in a compound is ZERO!!! The total charge of all the ions in a compound is ZERO!!!

Chemical Formulas A chemical formula tells you the type and number of atoms in the representative unit of a compound. A chemical formula tells you the type and number of atoms in the representative unit of a compound.

Writing Chemical Formulas 1 ) Write the symbol for the elements and their oxidation number, positive ion first (the metal). +2

Writing Chemical Formulas 2) Criss cross the numbers and write them as subscripts without the signs.

Writing Chemical Formulas 3) If there is a charge of one, do not write it. The one is implied.

Writing Chemical Formulas 4) If you have subscripts that are multiples, reduce them down. 42

Writing Chemical Formulas 5) If using polyatomic ions, put parentheses if there are more than one.

Examples 1. Barium & chlorine 2. Potassium & Nitrogen 3. Lithium & Phosphate 4. Iron (III) & Nitrate 5. Manganese (IV) & Sulfur

Naming Ionic Compounds For naming an ionic compound, 1) Name the metal. 2) Name the second element (the non-metal), but change the ending to –ide.

Naming Ionic Compounds If there is a polyatomic ion instead of a single nonmetal, just name the polyatomic ion, don’t change the ending!

Naming Ionic Compounds Example: Na 2 O Example: Na 2 O Sodium oxide Example: MgCl 2 Example: MgCl 2 Magnesium chloride Example Na 2 CO 3 Example Na 2 CO 3 Sodium carbonate

Naming Ionic Compounds 3) If a positive ion (a metal) can have more than one oxidation number, you have to designate its charge in the name!

Naming Ionic Compounds We do this by putting the charge as a Roman numeral in parenthesis between the positive and negative ion. Use the reverse criss cross method to determine what goes in parentheses.

Naming Ionic Compounds Example: Fe 2 O 3 Example: Fe 2 O 3 Iron (III) oxide Example: FeO (remember, oxygen’s oxidation number is 2-) Example: FeO (remember, oxygen’s oxidation number is 2-) Iron (II) oxide

Naming Ionic Compounds What elements that don’t need parentheses? 1) Group I, II and IIIA 2) Zn, Cd (always +2) 3) Ag (always +1)

Naming Ionic Compounds Which means that transition metals do need parentheses!

Naming Ionic Compounds Name the negative ion and: Name the negative ion and: If a nonmetal end in -ide; if not, end normally (polyatomic ion). If a nonmetal end in -ide; if not, end normally (polyatomic ion).

Name these: Na 2 S

Name these: Na 2 S sodium sulfide

Name these: Na 2 S sodium sulfide CuCl 2

Name these: Na 2 S sodium sulfide CuCl 2 copper (II) chloride

Name these: Na 2 S sodium sulfide CuCl 2 copper (II) chloride K 2 SO 4

Name these: Na 2 S sodium sulfide CuCl 2 copper (II) chloride K 2 SO 4 potassium sulfate

Name these: Na 2 S sodium sulfide CuCl 2 copper (II) chloride K 2 SO 4 potassium sulfate Pb(NO 3 ) 3

Name these: Na 2 S sodium sulfide CuCl 2 copper (II) chloride K 2 SO 4 potassium sulfate Pb(NO 3 ) 3 lead (III) nitrate