Aim: What are polar bonds and polar

molecules?

Polar and Nonpolar Bonds

• There are two types of covalent bonds• Nonpolar Covalent Bonds (share electrons equally)• Polar Covalent Bonds (share electrons unequally)

Polar Covalent Bond

• A Polar Covalent Bond is unequal sharing of electrons between two atoms (HCl)• In a polar covalent bond, one atom typically has a negative charge, and the other atom has a positive charge

Nonpolar Covalent Bond

• A Nonpolar Covalent Bond is an equal sharing of electrons between two atoms (Cl2, N2, O2)

Classification of Bonds

You can determine the type of bond between two atoms by calculating the difference in electronegativity values between the elements

The bigger the electronegativity difference the more polar the bond.

Type of Bond Electronegativity Difference

Nonpolar Covalent 0 0.4

Polar Covalent 0.5 1.9

Ionic 2.0 4.0

Practice

What type of bond is HCl? (H = 2.1, Cl = 3.1)

Your Turn To Practice N(3.0) and H(2.1)

H(2.1) and H(2.1)

Ca(1.0) and Cl(3.0)

Al(1.5) and Cl(3.0)

Mg(1.2) and O(3.5)

H(2.1) and F(4.0)

Difference = 3.1 – 2.1 = 1.0Therefore it is polar covalent bond.

How to show a bond is polar

• Isn’t a whole charge just a partial charge

• + d means a partially positive• - d means a partially negative

• The Cl pulls harder on the electrons• The electrons spend more time near the Cl

H Cl+d -d

Polar Molecules

• Molecules with a positive and a negative end• Requires two things to be true

The molecule must contain polar bonds This can be determined from differences in electronegativity.

Must determine symmetry first.

Symmetrical Molecules

• Because of symmetry, molecules that have polar bonds are overall a nonpolar molecules (+ and – charges cancel out or balance out)

• Examples:• CO2 BF3

• CCl4

Asymmetrical Molecules

• If a molecule has polar bonds (and there is no symmetry to cancel out + and – charges), the molecule is polar.

• Examples:• H2O HCl

• NH3

Dipole

When there is unequal sharing of electrons a dipole exists Dipole is a molecule that has two poles or regions with opposite chargesA dipole is represented by a dipole arrow pointing towards the more negative end

Practice Drawing Dipoles

P- Br

P = 2.1

Br = 2.8P –Br + -

Practice H(2.1) – S(2.5) F(4.0) - C(2.5) C(2.5) - Si(1.8) N(3.0) – O(3.5)

Is it Polar?

• HF

• H2O

• NH3

• CF4

• CO2