Polar Bonds and Polar Molecules

Question 1

Electronegativity

Answer 1

An element with a strong electron pulling power has a high electronegativity and an element with weak electron pulling power has low electronegativity. It is a relative measure and is best used to compare atoms. Electronegativity increases from left to right across periodic table and decreases down a period.

Question 2

Polar Bonds

Answer 2

Polar bonds are covalent bonds between two atoms where the electrons are shared unequally. A dipole is a permanent partial charge separation along a bond. When two atoms involved in a covalent bond have a different pull of electrons (electronegativity), the electrons in the bond are shared unequally. This creates a permanent dipole in the bond and the bond is called a polar covalent bond.

When the two atoms in a covalent bond have the same pull over electrons, the electrons in the bond are shared equally. As a result, there is no dipole and the bond is called a non-polar covalent bond.

0 - 0.4: Pure (nonpolar) covalent bond: electrons share equally

0. 4 - 2.0: Polar covalent bond: electrons shared unequally
1. 0 - 4.0: Ionic bond: electron transferre

Question 3

Polar Molecules

Answer 3

A polar molecule is a molecule in which one part of the molecule is slightly positve and another is slightly negative due to unequal electron distribution.

Most molecules can have more than one bond, so we need to think more carefully about whether or not a molecule is polar overall. In order to identify polar molecules:

1. Are there polar bonds present in the molecule?
2. What is the molecular geometry
3. Considering the shape, do the dipoles cancel out?