1. Unit 6, Lesson 9: Covalent Bonding and London Forces

2. Covalent Bonding
A covalent bond is a bond that involves the equal sharing of electrons.
It forms between two non-metals.
The atoms involved share one or more electrons in order to attain full electron shells.
Non-metals have large electronegativities, so they attract each other’s electrons strongly and won’t “let go” of their own.

3. Recap: Covalent vs. Ionic Bonds

4. Melting Points of Covalent Compounds
Covalent bonds are very strong.
Some covalent compounds form a network of covalent bonds connecting all of the atoms. These have high melting points.
Others only have covalent bonds within individual molecules. These have low melting points.

5. Strengths of Covalent Bonds
The more electrons shared in a bond, the _____ the bond, and the _____ the bond length.
The larger the atoms are, the _____ the bond.
10 min

6. Brain Break!

7. Formulae of Covalent Compounds
Rather than criss-crossing charges (as with ionic), criss-cross the valences!
Example: What compound will form from N and F?
Your turn: What compound will form from:
B and O? d) N and I?
P and O? e) C and Cl?
F and O?
10 min

8. London Forces
Intramolecular forces are strong forces within molecules, such as ionic and covalent bonds.
Intermolecular forces are weak forces between molecules, such as London forces.

9. London forces are weak attractive forces that arise from temporary dipole-dipole interactions between atoms.
A dipole is an uneven charge distribution across a molecule.

10. Strength of London Forces
The more total electrons in an atom or molecule, the stronger the London forces.
London forces are important when they’re the only force between two species.
This happens among closed-shell species, such as noble gas atoms and covalent molecules (ones that do not form networks).

11. Practice:
Pg. 182 #81 and 84
There’ll be a quiz next class on Lessons 7 to 9!
5 min