DETERMINING
POLARITY
Remember:
◦Electronegativity: describes how much an
atom wants an extra electron
Nonpolar Bonds
In a nonpolar bond, the atoms in the bond
pull equally on the electrons. This happens
when the atoms involved have almost the
same electronegativity value.
Examples: All diatomic molecules
Br I N Cl H O F
Polar Bonds
A polar bond results when there is an
unequal pull of electrons.
This happens when one atom is more
electronegative than another!
Ex: HF
Bond Polarity
Like magnets, covalent bonds can have a
“poles.”
This happens when one atom pulls electrons
closer to it’s nucleus than the surrounding
atoms.
This creates a positive
and negative end
Label the following bonds as polar or
nonpolar
◦ Br2
◦ CO
◦ HCl
◦ H2
Molecular Polarity
◦A molecule can be nonpolar even if polar
bonds are present!
◦This can happen when the polar bonds
have equal pull and “cancel” out due to
the molecule being symmetrical.
Molecular Polarity
◦ Nonpolar molecules are symmetrical
◦ No lone pairs on center atoms
◦ All the outside atoms are the same
◦ Polar molecules are not symmetrical
◦ At least 1 lone pair on center atom
◦ The outside atoms are NOT the same
Practice #1
◦ Draw the lewis structure of CH4
◦ What is the central atom?
◦ How many unshared pairs of electrons are on
the center atom?
◦ What shape is this molecule?
◦ Is the molecule polar or nonpolar?
Practice #2
◦ Draw the lewis structure of SBr2
◦ What is the central atom?
◦ How many unshared pairs of electrons are on
the center atom?
◦ What shape is this molecule?
◦ Is the molecule polar or nonpolar?
Worksheet #7 A – NCl3