1. Polar Covalent Bonds
Electron pairs in covalent bonds are not always shared equally
This affects the properties of the compound
Remember electronegativity?
The atom with the higher electronegativity attracts the bonding electrons more.
Electrons are pulled closer to this atom.

2. Example: HCl Draw the Lewis Structure for HCl
The bonding pair are pulled more towards the most electronegative atom...which one is that?

3. Review: Naming Binary Acids
These are covalent compounds
They do not contain oxygen
They are named using ionic naming conventions
Eg. HCl  hydrogen chloride
HBr  hydrogen bromide
HCN  hydrogen cyanide (not binary)
The form ions in water (this is why they are named like ionic compounds
To name when in water (aqueous)
Drop hydrogen, add “hydro” to root, change ending to “ic acid”
Hydrogen chloride  hydrochloric acid

4. IUPAC names for binary acids
The general form “aqueous hydrogen _______” is used
Eg. HCl  aqueous hydrogen chloride
HBr  aqueous hydrogen bromide

5. Space Filling Model of HCl
If we look at a model of HCl
We find that the bonding pair is
pulled more toward Cl
Cl becomes slightly – ( we use the symbol δ-)
H becomes slightly + ( we use the symbol δ+)
This small difference in charge within a covalent molecule is called a dipole

6. Polar Covalent Bonds
If a molecule has a dipole we refer to the bond as a polar covalent bond
The molecule itself is considered to be polar
The difference in electronegativity b/n the atoms involved determines how polar the bond will be.

7. Electronegativity difference
For F-H bonds
The electronegativity of H is 2.1
The electronegativity of F is 4.0
The electronegativity difference = = 1.9
This bond is very polar!
For C-H bonds
The electronegativity difference = = 0.4
This is only slightly polar

8. Determining the polarity of a bond
If the electronegativity difference is less than 0.5, the bond is considered slightly polar
Covalent bonds are completely non-polar only when the 2 atoms are identical
Eg. H2
The electronegativity difference is also called the ionic character of the bond

9. Is a bond polar covalent or ionic?
If the ionic character is > 1.7, the bond is considered to be ionic
It is hard to tell the difference between highly polar covalent bonds and ionic bonds
Therefore, we usually consider, metal + non-metal bonds to be ionic and non-metal + non-metal bonds to be covalent

10. Bonding Continuum

11. Predicting Polarity
For the following pairs of atoms, use electronegativity to determine if the bond will be non-polar, polar covalent or ionic
calcium and chlorine
nitrogen and bromine
carbon and fluorine
For the above pairs, indicate which atom will be slightly positive and which one will be slightly negative.
Determine the bond polarity in the compound IF. Is it slightly polar or very polar?