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.

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

Just like most things in nature, these

Na

1+ Cl

1-

NaCl

Ionic bonds

Ionic compounds have certain characteristics because of their ionic bonds: Most are crystalline solids at room

temperature. 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).

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. 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.

2+

1-

Ca2+

Cl -Cl -

CaCl2

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

CaCl2 calcium chloride

Science 10 – Nov. 24th

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?

Step 1 – Write the symbols of the elements with the metal first and non-metal second

Ca FStep 2 – Write the ion charge of each

element Ca2+ 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 S2) 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

Science 10 – Nov. 15th

Write the chemical formula and chemical name for the compound formed by chlorine and calcium.