IONIC COMPOUNDS Chapter 5.8 DAY 1

IONIC COMPOUNDS There are over one hundred elements in the periodic table, and thousands of different compounds are formed when these elements combine. VALENCE – elements in the same families tend to form ions with similar ionic charges. Also called combining capacity of an element.

Metals and nonmetals combine to form ionic compounds by transferring electrons. The metals atoms lose electrons to form positive ions The nonmetal atoms gain those electrons to form negative ions The result is a compound that is electrically neutral. The sum of the charges on the positive ions equals the sum of the charges on the negative ions.

WRITING FORMULAS OF IONIC COMPOUNDS EXAMPLE 1- What is the formula for the ionic compound of calcium and fluorine? Step 1 – Write the symbols of the elements with the metal first and non-metal second Ca F Step 2 – Write the ion charge of each element Ca+2 F-1

Step 3 – Determine how many of each you need to have an overall charge of zero. Ca+2 F-1 F-1 Step 4 - Write the formula using subscripts, after the element, to indicate how many you used. Ca1F2 CaF2 ( 1 is not needed )

EXAMPLE 2 What is the formula for the ionic compound of aluminum and sulfur? Steps: 1) Al S 2) Al+3 S-2 3) Al+3 Al+3 S-2 S-2 S-2 4) Al2S3

CRISS-CROSS RULE Al+3 S-2 Al2S3 Watch out for lowest terms: Mg+2 O-2 Mg2O2 MgO

WRITING NAMES OF IONIC COMPOUNDS When naming an ionic compound we simply write the name of the metal first and non-metal second. We change the ending of the non-metal name so that it ends in “ide.”

EXAMPLES 1) NaCl – sodium Chloride 2) CaBr2 – calcium bromide 3) MgO – magnesium oxide

HOMEWORK Read pages 192-194 Questions page 195 #1a, 3,4,5,6