Ionic Compounds Names and Formulas

Vocabulary Ion – an atom that has an electrical charge due to the gain or loss of electrons Monatomic – contains one (1) atom Polyatomic – contains 2 or more atoms Oxidation number – the charge on a monatomic atom

Positive Ions Positive ions form when electrons are lost Groups 1A, 2A, 3A, and the transition metals form positive ions. Oxidation numbers:  Group 1A is 1+  Group 2A is 2+  Group 3A is 3+

Negative Ions Negative ions form when electrons are gained. Groups 5A, 6A, and 7A form negative ions. Oxidation numbers:  Group 5A is 3-  Group 6A is 2-  Group 7A is 1-

More vocabulary Ionic Bond – The electrostatic force that holds oppositely charged particles together. Ionic Compound – a chemical compound formed by an ionic bond. Salt – a name for an ionic compound.

Properties of Salts 1. very hard – 2. high melting points – 3. brittle – each ion is bonded to several oppositely -charged ions many bonds must be broken with sufficient force, like atoms are brought next to each other and repel calcite

Naming Binary Ionic Compounds 1 st ion is the positive ion Use the element name 2 nd ion is the negative ion Take the element name, but change the ending to –ide. Examples: chlorine becomes ____________ sulfur becomes _____________

Naming Examples NaF MgCl 2 Al 2 O 3

Writing the Formula for a Binary Ionic Compound 1. Write the symbols for the ions. Include the oxidation numbers (charges). 2. Criss-cross the charges. The charge of one ion will become the subscript on the opposite ion. 3. Reduce the subscripts to a lowest-terms ratio. Note: the formula for an ionic compound gives the number of atoms in one formula unit.

Formula Examples aluminum chloride magnesium oxide

Polyatomic Ions Polyatomic ions are charged particles that have 2 or more atoms covalently bonded. A covalent bond is a chemical bond formed by the sharing of electrons. Polyatomic ions should be treated as a single unit. Example: SO 4 2- is the sulfate ion.

Naming Ionic Compounds containing Polyatomic Ions Cation – positive ion Anion – negative ion The cation: If it is a polyatomic ion, use the name of the ion as the first word. If it is a monatomic ion, use the element name.

The anion: If polyatomic, use the ion name as the second word. If monatomic, use the element name modified with the ending –ide. Examples: NH 4 Cl CaSO 4

Writing Formulas for Ionic Compounds with Polyatomic Ions Use the criss-cross technique that is used for the binary compounds. If the polyatomic ion needs a subscript, then place parentheses around the polyatomic ion. The subscript goes outside of the parentheses.

Examples sodium sulfate ammonium phosphate Iron (III) nitrate