Ionic bonding

1
Ionic bonding

• Bonding that results from the electrical
  attraction between large numbers of cations and
  anions.

2
Example - NaCl

• Look at page 151
• Na has an electronegativity of 0.9
• Cl has an electronegativity of 3.0
• The difference is 2.1 which is greater than 1.7,
  so it is ionic.

3
A degree of ionic character

• The range for electronegativiy difference for
  ionic bonding is 1.7 to 3.3.
• Greater the difference, the more ionic the bond
  is or the more ionic character.

4
Ionic bonding

• Most of the rocks and minerals
• 3D network of ions combined so that the charges
  balance out.
• When in combination, the ions are at lowest
  potential energy the crystal lattice.
• Orderly arrangement

5
Formula unit

• The chemical formula for the simplest unit in the
  crystal lattice.
• Is the simplest collection of atoms from which an
  ionic compounds formula can be established.
• Naming end in ide

6
Strength of ionic bonds

• Measured by lattice energy the energy released
  when one mole of the ionic crystal is formed from
  gaseous ions.

7

• In general, the attraction between formula units
  is stronger than the attraction between two
  molecular units.
• The strength of attraction between the basic
  units of molecular and ionic compounds give rise
  to different properties between the two types of
  bonds.

8
Comparison

• Ionic
• High melting points
• High boiling points
• Hard
• brittle
• Poor conductor solid - (electrons can not move)
• Conducts liquid
• Many Dissociate in water

• Covalent
• Low melting points
• Low boiling points (gases at room temp)

9
Polyatomic ions

• A charged group of covalently bonded atoms. Pg
  210

10
Binary ionic compounds

• Charges have to balance out
• Figure out the expected charge on the element.
• (Oxidation state)
• Look at the subscripts
• Make adjustments to subscripts
• NEVER CHANGE THE OXIDATION STATE or (charge).