1. Mr. Samaniego Lawndale High School
Covalent Bonding
Edited By Ms. Locke at AVECHS
The unspoken hero: “Covalent Bond” 
Mr. Samaniego
Lawndale High School

2. Remember Ionic Bonds?
We learned about electrons being transferred (“given up” or “stolen away”)
This type of “tug of war” between a METAL and NONMETAL is called an IONIC BOND, which results in a SALT being formed

3. Molecular Compounds
In this chapter, you will learn about another type of bond in which electrons are shared
Covalent Bonds are atoms held together by SHARING electrons between NONMETALS

4. Monatomic vs. Diatomic Molecules
Most molecules can be monatomic or diatomic
Diatomic Molecule is a molecule consisting of two atoms
There are 7 diatomic molecules (SUPER 7) – N2, O2, F2, Cl2, Br2, I2, H2
You can also remember them as: H2O2F2Br2I2N2Cl2

5. Properties of Molecular Compounds
Liquids or gases at room temperature
Lower Melting Points than Ionic Compounds (which means that they are weaker than ionic)

6. Molecular Formulas
The Molecular Formula is the formula of a molecular compound
It shows how many atoms of each element a molecule contains
Example
H2O contains 3 atoms (2 atoms of H, 1 atom of O)
C2H6 contains 8 atoms (2 atoms of C, 6 atoms of H)

7. Practice
How many atoms total and of each do the following molecular compounds contain? H2 CO
CO2
NH3
C2H6O

9. Ionic versus Covalent IONIC COVALENT Bonded Name Salt Molecule
Bonding Type
Transfer e-
Share e-
Types of Elements
Metal & Nonmetal
Nonmetals
Physical State
Solid
Solid, Liquid, or Gas
Melting Point
High (above 300ºC)
Low (below 300 ºC)
Solubility
Dissolves in Water
Varies
Conductivity
Good
Poor

10. Covalent Bonding
Remember that ionic compounds transfer electrons in order to attain a noble gas electron configuration
Covalent compounds form by sharing electrons to attain a noble gas electron configuration
Regardless of the type of bond, the Octet Rule still must be obeyed (8 valence electrons)

11. Single Covalent Bond
A Single Covalent Bond consists of two atoms held together by sharing 1 pair of electrons (2 e-)

12. Electron Dot Structure

13. Shared versus Unshared Electrons
A Shared Pair is a pair of valence electrons that is shared between atoms
An Unshared Pair is a pair of valence electrons that is not shared between atoms

14. Practice Lewis Dot Structures
Chemical Formula
# of Valence Electrons
Single Line Bond Structure
# of Remaining Electrons
Lewis Dot Structure
Octet Check All Atoms=8
Hydrogen=2 F2
H2O
NH3
CH4

15. Double Covalent Bonds
Sometimes atoms attain noble gas configuration by sharing 2 or 3 pairs of electrons
A Double Covalent Bond is a bond that involves 2 shared pairs of electrons (4 e-)

16. Triple Covalent Bond
A Triple Covalent Bond is a bond that involves 3 shared pairs of electrons (6 e-)

17. Covalent Bonds

18. Practice Lewis Dot Structure
Chemical Formula
# of Valence Electrons
Single Line Bond Structure
# of Remaining Electrons
Lewis Dot Structure
Octet Check All Atoms=8
Hydrogen=2 O2
CO2 N2
HCN

19. Bond Dissociation Energy
Bond Dissociation Energy is the energy required to break a bond between two atoms
A large bond dissociation energy corresponds to a strong bond which makes it unreactive
Carbon has strong bonds, which makes carbon compounds stable and unreactive

20. Polar Bonds and Molecules
There are two types of covalent bonds
Nonpolar Covalent Bonds (share equally)
Polar Covalent Bonds (share unequally)

21. Polar Covalent
A Polar Covalent Bond is unequal sharing of electrons between two atoms (HCl)
In a polar covalent bond, one atom typically has a negative charge, and the other atom has a positive charge

22. Nonpolar Covalent Bond
A Nonpolar Covalent Bond is equal sharing of electrons between two atoms (Cl2, N2, O2)

24. Classification of Bonds
You can determine the type of bond between two atoms by calculating the difference in electronegativity values between the elements
Type of Bond
Electronegativity Difference
Nonpolar Covalent
0  0.4
Polar Covalent
0.5  1.9
Ionic
2.0  4.0

25. Practice Your Turn To Practice
What type of bond is HCl? (H = 2.1, Cl = 3.1)
Difference = 3.1 – 2.1 = 1.0
Therefore it is polar covalent bond.
Your Turn To Practice
N(3.0) and H(2.1)
H(2.1) and H(2.1)
Ca(1.0) and Cl(3.0)
Al(1.5) and Cl(3.0)
Mg(1.2) and O(3.5)
H(2.1) and F(4.0)

26. Dipole
No bond is purely ionic or covalent … they have a little bit of both characters
When there is unequal sharing of electrons a dipole exists
Dipole is a molecule that has two poles or regions with opposite charges
A dipole is represented by a dipole arrow pointing towards the more negative end

27. Practice Drawing Dipoles
P- Br
P = 2.1
Br = 2.8
P –Br
 -
Practice
H(2.1) – S(2.5)
F(4.0) - C(2.5)
C(2.5) - Si(1.8)
N(3.0) – O(3.5)

28. Attractions Between Molecules
Besides ionic, metallic, and covalent bonds, there are also attractions between molecules
Intermolecular attractions are weaker than ionic, covalent, and metallic bonds
There are 2 main types of attractions between molecules: Van der Waals and Hydrogen

29. Van der Waals Forces
Van der Waals forces consists of the two weak attractions between molecules
1. dipole interactions – polar molecules attracted to one another
2. dispersion forces – caused by the motion of electrons (weakest of all forces)

30. Hydrogen Bond
Hydrogen Bonds are forces where a hydrogen atom is weakly attracted to an unshared electron pair of another atom

31. Hydrogen Bond
This other atom may be in the same molecule or in a nearby molecule, but always has to include hydrogen
Hydrogen Bonds have about 5% of the strength of an average covalent bond
Hydrogen Bond is the strongest of all intermolecular forces

32. Intermolecular Attractions
A few solids that consist of molecules do not melt until the temperature reaches 1000ºC or higher called network solids (Example: diamond, silicon carbide)
A Network Solid contains atoms that are all covalently bonded to each other
Melting a network solid would require breaking bonds throughout the solid (which is difficult to do)