IONIC COMPOUNDS Chapter 5.8

IONIC COMPOUNDS Recall: Metals form positive ions (+) and non-metals form negative ions (-). Na 1+ Cl 1-

IONIC COMPOUNDS When ions like NaCl form, they make an ionic bond. When ions like NaCl form, they make an ionic bond. Ionic bond – the attraction between a positive metal ion and a negative non- metal ion. Ionic bond – the attraction between a positive metal ion and a negative non- metal ion. Na 1+ Cl 1-

Like most ionic compounds, NaCl can form a crystalline structure Like most ionic compounds, NaCl can form a crystalline structure Just like most things in nature, these Just like most things in nature, these Na 1+ Cl 1- NaCl

Ionic bonds Ionic compounds have certain characteristics because of their ionic bonds: Ionic compounds have certain characteristics because of their ionic bonds: Most are crystalline solids at room temperature. Most are crystalline solids at room temperature. Ionic compounds generally have high melting points. Ionic compounds generally have high melting points. Can conduct an electric current when dissolved in water (electricity can “jump” between the negative and positive charges). Can conduct an electric current when dissolved in water (electricity can “jump” between the negative and positive charges).

Just like most things in nature, the charges in ionic compounds must balance out. Just like most things in nature, the charges in ionic compounds must balance out. Ex. Sodium ion is 1+, Chloride ion is 1- so they balance out. Ex. Sodium ion is 1+, Chloride ion is 1- so they balance out. What about calcium and chloride? What about calcium and chloride? Na 1+ Cl 1- NaCl

Calcium atom becomes Calcium ion with a charge of _____. Chlorine atom becomes Chloride ion with a charge of _____. So how will they form a compound? One calcium ion will bond with two chloride ions so that the charges balance out Ca 2+ Cl -  CaCl 2

Recall – use subscripts to show how many of each atom are in a compound. Recall – use subscripts to show how many of each atom are in a compound. CaCl 2 calcium chloride

Science 10 – Nov. 24 th Draw Bohr diagrams for atoms and stable ions for: Mg, S, Na, F Draw Bohr diagrams for atoms and stable ions for: Mg, S, Na, F

WRITING FORMULAS OF IONIC COMPOUNDS EXAMPLE 1- What is the formula for the ionic compound of calcium and fluorine? 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 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. Ca 1 F 2 CaF 2 ( 1 is not needed )

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

CRISS-CROSS RULE Al +3 S -2 Al +3 S -2 Al 2 S 3 Al 2 S 3 Watch out for lowest terms: Watch out for lowest terms: Mg +2 O -2 Mg +2 O -2 Mg 2 O 2 MgO Mg 2 O 2 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.” 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 1) NaCl – sodium Chloride 2) CaBr 2 – calcium bromide 2) CaBr 2 – calcium bromide 3) MgO – magnesium oxide 3) MgO – magnesium oxide

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

Science 10 – Nov. 15 th Write the chemical formula and chemical name for the compound formed by chlorine and calcium. Write the chemical formula and chemical name for the compound formed by chlorine and calcium.