1. Ionic Bonding

2. Ionic Bond
Chemical bond resulting from electrostatic attraction between positive and negative ions.
Goal: achieve stable octet of electrons (noble gas configuration)
Illustrate by
Orbital notation
Lewis Dot diagrams

3. Show transfer of VALENCE electrons to achieve octet
But WHICH electrons (i.e. what orbitals) are involved?
                                                                   
Formation of
The Octets
A quantum mechanical representation of the electron transfer

4. Three Types of Bonding Ionic Covalent Metallic
electrons are transferred.
Covalent
electrons are shared.
Metallic
“sea of mobile electrons.”

5. Identify Bond Type from Formula
Ionic Compounds
metal + nonmetal
Covalent Compounds
nonmetal + nonmetal
Metallic
metal symbol
Salts

6. Na metal 
Cations
Metals lose e-

7. Anions
Nonmetals gain e-
Cl2 (g) 

8. Ionic Compounds metal + nonmetal
Composed of positive and negative ions combined so that compound is NEUTRAL.
Most ionic compounds are …
crystalline solids.
Expressed as Formula Units, not molecules (which are covalent)!
Simplest ratio of atoms (empirical formula)
metal + nonmetal

9. Structure of Ionic Compounds
Ions are attracted to each other by strong electrostatic interactions.
Form a crystal lattice
a regular 3-D pattern or array.
Ions are held in fixed positions in the solid state.
Unit Cell = smallest repetitive unit in lattice

10. Strength of Ionic Bond Na+(g) + Cl−(g) → NaCl(s) Lattice Energy
Energy released when one mole of an ionic crystalline compound is formed from gaseous ions.
Na+(g) + Cl−(g) → NaCl(s)
The experimental lattice energy of NaCl is −787 kJ/mol.
Shown as negative value  Exothermic

11. Electron is transferred from Na to Cl
Tiger Graphic

12. Oxidation Number
Determines how many atoms are needed to form the ionic compound.

13. Properties of Ionic Compounds
Memorize!
High melting points
Low vapor pressures
Solids do not conduct electricity
Melts (liquids) do conduct electricity
Solutions (aq) conduct electricity
electrolytes: substances whose water solution conducts an electric current.
Tend to be hard and brittle
High solubility in water.

14. Aside: What Conducts Electricity?
***MOBILE CHARGED PARTICLES***
If something conducts a current, it has some kind of mobile charged particles: either electrons (solids) or ions (solutions).
If something doesn’t conduct, it doesn’t have particles that are both mobile and charged.
Memorize this!

15. Linus Pauling 1954 Nobel Prize Chemistry
First to show that chemical bonds could show degrees of both a covalent and ionic nature.
Led to the development of electronegativity values.

16. Electronegativity Difference
1.7

17. Electronegavitity Difference
Bonding between atoms is a continuum from ionic to covalent.
The larger the difference in electronegativity between two bonded elements, the more ionic in character the bond has.
Which has more ionic character?
CaO or KF or LiH

18. Bonding Character