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)