Bond Polarity

Connecting to you

• Snow covers approximately 23% of Earth’s surface. Each individual snowflake is formed from as many as 100 snow crystals. The size and shape of each crystal depends on the air temperature at the time the snow crystal forms. In this section, you’ll see that the polar bonds in water molecules influences the distinctive geometry of snowflakes.

Bond polarity

• What is the difference between covalent bonding and ionic bonding?

• The bonding pairs of electrons in covalent bonds are not always shared equally. Why would this be the case?

Electronegativity

• The ability to attract electrons• Not all atoms have the same “attractability” so

therefore they will pull with different strengths.

Nonpolar covalent bond

• When the atoms of a bond pull equally and therefore all electrons are shared equally.

• Examples: O2, H2, N2

Polar covalent bond

• The more electronegative atom attracts electrons more strongly and gains a slightly negative charge. The less electronegative gains a slight positive charge.

• Example: H2O, HCl

Polar molecules

• In a polar molecule, one end of the molecule is slightly negative and the other is slightly positive.

Attractions between molecules

• What holds a solution together?

• Intermolecular forces are weaker than ionic or covalent bonds. – Van der Waals forces• Dipole interactions• Dispersion forces

– Hydrogen bonding

Dipole interactions

• When polar molecules are attracted to one another due to their dipole moments

Dispersion forces

• The weakest of all IM forces. • Occur between non-polar molecules.

Hydrogen bonding

• Not really bonding at all• Attractive forces in which a hydrogen

covalently bonded to highly electronegative atom is also weakly bonded to an unshared pair of another electronegative atom. – Example: Water– Demonstration

Demonstration

Exit slip

• How does electronegativities affect polar bonds?

• Not every molecule with polar bonds is actually polar. Explain this statement.

• Predict what intermolecular force would hold a solution of HBr molecules together.