Warm Up

Give the formula that will result from reacting the following ions:

1.Na+, O2-

2.Al3+, Cl-

3.Mg2+, N3-

4.Al3+, S2-

5.Ca+, Br -

1.Na2O sodium oxide2.AlCl3 aluminum chloride3.Mg3N2 magnesium nitride4.Al2S3 aluminum sulfide5.No such thing as Ca+, can only

be 2+ cation

Ionic Bonds and Compounds

Section 7.2

• Understand how ionic bonds are formed

• Know that ionic compounds come from cation and anion attraction to each other

• Get a feel for the structure and properties of ionic solids

Learning Objectives

• Chemical bond: attractive force holding two or more atoms together.

• Covalent bond results from sharing electrons between the atoms. Usually found between nonmetals.

• Ionic bond results from the transfer of electrons from a metal to a nonmetal.

• Metallic bond: attractive force holding pure metals together.

Overview of Bonding

Ionic Bonds

• An ionic bond is typically formed between a metal and a non-metal. 

• Metals have low electronegativities (less than 2.0), while non-metals have high electronegativities (above 2.0).

• Consequently, the non-metal is "stronger" than the metal, and can steal electrons very easily from the metal. 

• This results in the metal becoming a cation, and the non-metal becoming an anion.

Ionic Bonds

Ionic Bonds

Ionic Bonds

Ionic bonds are not about sharing electrons rather ….

The more electronegative element (anion to be) simply steals the electron(s) from the more electropositive element (cation to be).

Ionic Bonds

Ionic Bonds-Simple Animation

Sodium Fluoride

Ionic Compound Structure

Ionic Compound Structure

Ionic Compounds

Cations and anions are attracted by electrostatic forces to form ionic bonds

Bonding occurs to create an electrically neutral ionic compound

Chemical formula for ionic compounds called formula unit

Properties of Ionic Crystals

Most ionic compounds are crystals at room temperature

Attraction of + and - ions results in a stable structure = high melting temperature

Ionic vs. Covalent

Ionic CovalentCompounds Compounds

–Gases, liquids, or solids–Low melting and boiling points-moth balls–Poor electrical conductors

–Many soluble in nonpolar liquids but not in water

– Crystalline solids– High melting and

boiling points– Conduct electricity

when melted– Many soluble in

water but not in nonpolar liquid

Coordination Number

Coordination number is the number of ions of opposite charge that surround the ion in a crystal

Pretty Ionic Solids

CaF2 (fluorite)HgS (cinnabar) FeS2 (pyrite)

PbMoO4 (wulfenite)CaCO3 (aragonite) TiO2 (rutile)