7.2 Ionic Compounds and Bonding

Warm Up
Give the formula that will
result from reacting the
following ions:
1. Na+, O2-
2. Al3+, Cl3. Mg2+, N3-
4. Al3+, S25. Ca+, Br -
1. Na2O
sodium oxide
2. AlCl3
aluminum chloride
3. Mg3N2
magnesium nitride
4. Al2S3
aluminum sulfide
5. No such thing as Ca+, can only
be 2+ cation
Ionic Bonds and
Section 7.2
Learning Objectives
• 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
Overview of Bonding
• Chemical bond: attractive force holding two or
more atoms together.
• Covalent bond results from sharing electrons
between the atoms. Usually found between
• Ionic bond results from the transfer of electrons
from a metal to a nonmetal.
• Metallic bond: attractive force holding pure metals
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
 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
Ionic vs. Covalent
– Crystalline solids
– High melting and
boiling points
– Conduct electricity
when melted
– Many soluble in
water but not in
nonpolar liquid
–Gases, liquids, or solids
–Low melting and boiling
points-moth balls
–Poor electrical conductors
–Many soluble in nonpolar
liquids but not in water
Coordination Number
 Coordination number is the
number of ions of opposite charge
that surround the ion in a crystal
Pretty Ionic Solids
CaF2 (fluorite)
PbMoO4 (wulfenite)
HgS (cinnabar)
FeS2 (pyrite)
CaCO3 (aragonite)
TiO2 (rutile)

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