SECTION 6–3:NAMING COMPOUNDS AND WRITING FORMULAS

Physical Science

OBJECTIVES

Recognize and describe binary ionic compounds, metals with multiple ions, and polyatomic ions.

Name and determine chemical formulas for ionic and molecular compounds.

DESCRIBING IONIC COMPOUNDS

The name of an ionic compound must distinguish the compound from other ionic compounds containing the same elements. The formula of an ionic compound describes the ratio of the ions in the compound.

Red copper oxide

Black copper oxide

BINARY IONIC COMPOUNDS A compound that contains only two

elements is called a binary compound. We can easily name an ionic binary

compound by using the name of the cation and the name of the ion.

If we have a compound that contains sodium and chlorine would be called “sodium chloride.” It doesn’t matter how many atoms of each there are.

The name for the anion uses part of the name of the nonmetal with the suffix –ide.

Remember anion has a negative charge

BINARY IONIC COMPOUNDS

BINARY IONIC COMPOUNDS

Sodium chloride NaCl Aluminum oxide Al2O3 Beryllium iodide BeI2 Magnesium sulfide Mg2S Calcium nitride Ca3N2 Boron fluoride BF3

METALS WITH MULTIPLE IONS Most transition metals have more than one

charge. For instance, copper can have a 1+ or a 2+ charge. Iron can have a 2+ or 3+ charge.

ALL transition metals will have a positive charge!

When we name a compound with a transition metal that has more than one charge, we indicate the charge with a roman numeral: Copper (I) sulfide Cu2S Copper (II) sulfide CuS

POLYATOMIC IONS

A covalently bonded group of atoms that has a positive or negative charge and acts as a unit is a polyatomic ion.

For example, (OH)- is the hydroxide ion. It has a 1- charge.