Covalent Bonding

• In ionic bonding, electrons were transferred to other atoms.

• In covalent bonding, electrons are shared between atoms.

• We represent covalent compounds with electron dot diagrams. (Another short cut!)

• The number of dots around an atom is the same as the number of valence electrons. (The same as the group number)

• Ex.

Steps in Electron Dot Diagrams (EDD for short)

Example A. Hydrogen forms a covalent bond with another hydrogen atom to form a hydrogen molecule H2

1. Figure out how many atoms of each element you need. Draw the electron dot diagram for each of the atoms separately.

2. Decide how many electrons each atom wants to GAIN to have a full outer energy level! (usually occurs between nonmetals who want to gain electrons).

Each H atom wants to gain 1 to have a full outer energy level!

3. Line up the electrons to get ready to share.

4. For each two electrons that will be shared, replace the dots with a bond (a line). Continue until each is atom “happy” when you count shared and any remaining valence electrons.

Example B.

• Hydrogen and oxygen bond covalently to form a water molecule: H20

1) Figure out how many atoms of each element you need. Draw the electron dot diagram for each of the atoms separately.

2. Decide how many electrons each atom wants to GAIN to have a full outer energy level! (usually occurs between nonmetals who want to gain electrons).

- Each H wants to gain 1- O wants to gain 2

3. Line up the electrons to get ready to share.

4. For each two electrons that will be shared, replace the dots with a bond (a line). Continue until each is atom “happy” when you count shared and any remaining valence electrons.

Example C

• Two molecules of oxygen bond covalently to form an oxygen molecule O2

1) Figure out how many atoms of each element you need. Draw the electron dot diagram for each of the atoms separately.

2. Decide how many electrons each atom wants to GAIN to have a full outer energy level! (usually occurs between nonmetals who want to gain electrons).

- Each O wants to gain 2 electrons

3. Line up the electrons to get ready to share.

4. For each two electrons that will be shared, replace the dots with a bond (a line). Continue until each is atom “happy” when you count shared and any remaining valence electrons.

Example D

Carbon and Oxygen bond covalently to form carbon dioxide: CO2

1) Figure out how many atoms of each element you need. Draw the electron dot diagram for each of the atoms separately.

2. Decide how many electrons each atom wants to GAIN to have a full outer energy level!

Each O wants to gain 2

C wants to gain 4

3. Line up the electrons to get ready to share.

4. For each two electrons that will be shared, replace the dots with a bond (a line). Continue until each is atom “happy” when you count shared and any remaining valence electrons.

• SKIP Practice EDDs #1-6• Do the WS “Covalent Bonding Practice #2”• Check with key at the Kiosk