1. Covalent Bonds: Notes 5-3
Key Ideas:
1. What holds covalently boned atoms together?
2. What are the properties of molecular compounds?
3. How does unequal sharing of electrons affect molecules? - + + -

2. COVALENT BOND
A force that bonds two atoms together by a sharing of electrons Each pair of shared electrons creates a bond Usually occurs between atoms of non-metals H O H
Example – Water (H2O) - - - - + - + + - - - - -

3. How Covalent Bonds Form

4. How Covalent Bonds Form
The oxygen atom in water and the nitrogen atom in ammonia each have eight valence electrons as a result of forming covalent bonds with hydrogen atoms.

5. How Covalent Bonds Form
Double and triple bonds can form when atoms share more than one pair of valence electrons.

6. Types of Covalent Bonds
Different covalent bond types share a different number of valence electrons
Water (H2O)
Carbon Dioxide (CO2)
Nitrogen (N2)
Single Bonds Share 2 Electrons
Double Bonds Share 4 Electrons
Triple Bonds Share 6 Electrons

7. Unequal Sharing : Polar Covalent Bond
The unequal sharing of valence electrons between two atoms that gives rise to negative and positive regions of electric charge
Results from an atom’s electronegativity – the ability to attract electrons to itself
A molecule in which the polar covalent bonds does not cancel out will be polar. + + + +
Electron
Cloud
Bonded hydrogen
atoms showing
equal sharing of
electrons
Hydrogen and
fluorine bond with
an unequal sharing
of electrons
Why do you think the two Hydrogen atoms share
equally, but the Hydrogen and fluorine do not?

8. Unequal Sharing of Valence Electrons Versus Equal Sharing
In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does, so the bond formed is polar.
Fluorine forms a nonpolar bond with another fluorine atom.
A covalent bond is called nonpolar if the atoms equally share one or more pairs of electrons

9. Unequal (Polar) Versus Equal (Nonpolar) Sharing of Electrons
A water molecule is a polar molecule because of its bent shape.
A carbon dioxide molecule is a nonpolar molecule because of its straight-line shape.

10. Results of Bonding
Molecule A neutral group of two or more non-metal atoms held together by covalent bonds Type: Diatomic - molecules consisting of two atoms of the same element bonded together Examples: H2, F2, O2, N2
Compound A pure substance composed of two or more different elements (atoms) that are chemically combined Examples: CO, NO2, NaCl

11. Molecule, Compound, or Both?
Nitrogen
Cl2
Chlorine
NO2
Nitrogen Dioxide
CO2
Carbon Dioxide O2
Oxygen
CH4
Methane H2
Hydrogen NO
Nitric Oxide
H2O
Water