Academic Chemistry
Mr. Gensits
Class Notes
11/10/2015
Ionic Bonds and Ionic Compounds
Atoms must collide in order for a chemical reaction to occur.
The electron clouds between the two elements interact.
The nuclei of atoms are not changed in chemical reactions.
Atoms that have complete electron energy levels are stable.
Compounds composed of cations and anions are called ionic
compounds.
Ionic compounds are usually composed of metal cations and
nonmetal anions.
Although they are composed of ions, ionic compounds are
electrically neutral. The total positive charge is equal to the
total negative charge.
The oppositely charged ions are attracted to one another by
means of extremely strong electrostatic forces.
These electrostatic forces that hold together the ionic
compound are called ionic bonds.
Formula Units
A chemical formula shows the kinds and numbers of atoms in
the smallest representative unit of a substance.
An ionic compound consists of a collection of positively and
negatively charged ions arranged in repeating patterns.
The formula unit is the lowest whole number ratio of ions in
an ionic compound.
Crystal – forms because of the regular repeating arrangement
of atoms, ions, or molecules.
Properties of Ionic Compounds
High melting points
Hard
Brittle
Composed of well-organized, tightly bound ions
Strong, three dimensional crystal structure
Crystalline solids at room temperature
Tend to be soluble in water
Conduct electricity when dissolved in water and when melted
Coordination Number – the number of ions of opposite charge
that surrounds the ion in a crystal.
The coordination number is always the same for any given
ionic compound.
The coordination number for Na+ ions in NaCl is 6.
The coordination number for Cl- ions in NaCl is 6.
The coordination number for Cs+ ions in CsCl is 8.
The coordination number for Cl- ions in CsCl is 8.
The coordination number for Ti4+ ions in TiO2 is 6.
The coordination number for O2- ions inTiO2 is 3.
Electrolyte – any substance that conducts an electrical
current when dissolved in water or melted.