chemistry high school covalent bonding

1. SECTION 5: ELECTRONEGATIVITY AND
POLARITY
A chemical bond’s character is related to each
atom’s attraction for the electrons in the bond.
K
What I Know
W
What I Want to Find Out
L
What I Learned

2. Essential Questions
• How is electronegativity used to determine bond type?
• How do polar and nonpolar covalent bonds and polar
and nonpolar molecules compare and contrast?
• What are the characteristics of covalently bonded
compounds?

3. Review
• electronegativity
Vocabulary
New
• polar covalent bond

4. Electronegativity and Bond Character
• Electron affinity measures the tendency of an atom to accept
an electron.
• Noble gases are not listed because they generally do not
form compounds.
Electronegativity and Polarity
Copyright © McGraw-Hill Education

5. Electronegativity and Bond Character
• This table lists the character and type of
chemical bond that forms with differences in
electronegativity.

6. Electronegativity and Bond Character
• Unequal sharing of electrons results in a polar covalent
bond.
• Bonding is often not clearly ionic or covalent.
• This graph summarizes the range of chemical bonds
between two atoms.

7. Polar Covalent Bonds
• Polar covalent bonds form when atoms pull on electrons in a
molecule unequally.
• Electrons spend more time around one atom than another
resulting in partial charges at the ends of the bond called a
dipole.

8. Polar Covalent Bonds
• Covalently bonded molecules are either polar or non-polar.
• Non-polar molecules are not attracted by an electric field.
• Polar molecules align with an electric field.
• Compare water, H2O, and CCl4.
• Both bonds are polar.
• The molecular shapes, determined by VSEPR, is bent and tetrahedral,
respectively.
• O – H bonds are asymmetric in water, so they have a definite positive
end and a definite negative end. Thus, polar. The C – Cl bonds are
symmetrical in CCl4. The electric charge measured at any distance from
the center is identical on all sides and partial charges are balanced. Thus
nonpolar.

9. Polar Covalent Bonds
• Note: If bonds are polar, asymmetrical molecules are
polar, and symmetrical molecules are nonpolar.

10. Polar Covalent Bonds
• Solubility is the property of a substance’s ability to dissolve
in another substance.
• Polar molecules and ionic substances are usually soluble in
polar substances.
• Non-polar molecules dissolve only in non-polar substances.

11. Properties of Covalent Compounds
• Covalent bonds between atoms are strong, but attraction forces between
molecules are weak.
• The weak attraction forces are known as van der Waals forces.
• The forces vary in strength but are weaker than the bonds in a molecule
or ions in an ionic compound.
• Non-polar molecules exhibit a weak dispersion force, or induced dipole.
• The force between two oppositely charged ends of two polar molecules is
a dipole-dipole force.
• A hydrogen bond is an especially strong dipole-dipole force between a
hydrogen end of one dipole and a fluorine, oxygen, or nitrogen atom on
another dipole.

12. Properties of Covalent Compounds
• Many physical properties are due to intermolecular forces.
• Weak forces result in the relatively low melting and boiling
points of molecular substances.
• Many covalent molecules are relatively soft solids.
• Molecules can align in a crystal lattice, similar to ionic solids
but with less attraction between particles.
• Solids composed of only atoms interconnected by a network of
covalent bonds are called covalent network solids.
• Quartz and diamonds are two common examples of network
solids.

13. Review
Essential Questions
• How is electronegativity used to determine bond type?
• How do polar and nonpolar covalent bonds and polar and
nonpolar molecules compare and contrast?
• What are the characteristics of covalently bonded
compounds?
Vocabulary
• polar covalent bond