Ionic Bonds

08/29 & 08/30

Catalyst• Complete the Chart

Objectives

• I can explain how electrons are transferred in an ionic bond.

• I can explain that ionic compounds form crystals.

• I can use the octet rule and the Criss Cross rule to predict how ionic bonds will form.

Think Box:

• Look at your chart above. Do metals form anions or cations? Do nonmetals form anions or cations?

• Answer: Metals form positive cations. Nonmetals for negative anions.

An ionic bond is the electrostatic attraction between oppositely charged ions. eg. Na+ and Cl-

Notes: What is an ionic compound?

Ionic compounds form when electrons are transferred from a metal cation to a non-metal anion.

Notes: What is an ionic compound?

An ionic compound is made up of a metal and a non-metal.

Notes: What is an ionic compound?

Sodium + ChlorineSodium Chloride

Lithium + HydrogenLithium Hydride

Aluminum + OxygenAluminum Oxide

Ionic compounds form a crystal lattice structure.

Sodium + ChlorineSodium Chloride

Silver + BromineSilver Bromide

Magnesium + TelluriumMagnesium Telluride

Even though ions have a charge, ionic compounds are neutral overall.

ExamplesNa+ + Cl− → NaClLi+ + H− → LiHCa2+ + F- → CaF2

Al3+ + O2- → Al2O3

Ionic compound names: list the metal first, then the nonmetal. Change the last syllable of the nonmetal to –ide. If the metal forms more than one cation (transition metals) indicate the ion formed with a roman numeral.

ExamplesNa+ + Cl− → NaCl Sodium ChlorideLi+ + H− → LiH Lithium HydrideCa2+ + F- → CaF2 Calcium FluorideAl3+ + O2- → Al2O3 Aluminum OxideAg2+ + O2- → AgO Silver (II) Oxide

If ionic compounds are really large collections of ions in a crystal lattice structure, why do we write equations and chemical formulas showing just a few ions?

Think Pair Share

ExamplesNa+ + Cl− → NaClLi+ + H− → LiHCa2+ + F- → CaF2

Al3+ + O2- → Al2O3

Compound formulas show the proportion of cations to anions in an ionic compound.

The proportion is based on an overall neutral compound.

Use the Kris-Cross rule to find the correct proportion.

Kris Kross Method!

Ca3As2

Ca2+As3-

Just kris kross the positive and the negative charges

Na1+Cl1- NaCl

Pb4+O2- Pb2O4

Calcium and FluorineStep 1: Use the octet rule to write the ions separately.Step 2: Kris-Cross the charge to make subscripts.

Writing Compound Formulas Example

Ca2+ F-

CaF2The subscripts shows the proportion of cations to anions. Here, it is 1:2.

List the original ions, the chemical formula for the compound formed (with the correct proportions of ions for an overall neutral charge), and the compound name.

1. Sodium and Chlorine

Ionic Bonding Practice

Na+ Cl-

NaClSodium Chloride