1. COVALENT BONDING & CHEMICAL FORMULA
Vocabulary
Chemical Formula
Molecular Compound
Molecular Formula
Molecule
Ionic compound
Formula Unit
Bond Energy
Electron Dot Notation
Lewis Structure
Structural Formula
Covalent Bond
Electronegativity
Single Bond
Double Bond
Multiple Bond

2. COVALENT BONDING & CHEMICAL FORMULA
A little Review: What is a Chemical Formula?
Indicates # of atoms of each element in a compound using the element Symbols and subscripts
Examples:
H2O
NaCl

3. COVALENT BONDING & CHEMICAL FORMULA
A little Review: What is the difference between a MOLECULAR FORMULA & a FORMULA UNIT ?
CHEMICAL FORMULA
Molecular Compounds
(Covalent)
Ionic Compound – Compound created by transferring electrons
Molecular Formula - Formula for a stable group of atoms which exists as a package.
Unit Formula- simplest part of a crystal structured compound

4. COVALENT BONDING & CHEMICAL FORMULA
A little Review: What is the difference between a MOLECULAR FORMULA & a FORMULA UNIT ?
1 Cl
1 Na
Ionic compounds are part of a geometric crystal structure. The Unit formula is the most simple component of the structure which repeats
Unit Formula: NaCl
Molecules act as individual lumps of substance.
Molecular Formula: H2O

5. COVALENT BONDING & CHEMICAL FORMULA
A little Review: What is a Chemical Formula?
Indicates # of atoms of each element in a compound using the element Symbols and subscripts
Examples:
H2O
NaCl

6. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
Its all about sharing Electrons
Some atoms share nicely (equally)
. ..while some atoms do not share equally or not at all.

7. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
How can you tell how well the atoms are sharing?
Electronegativity tells how much atoms take electrons
Higher Electonegative Atoms keep electrons more
Low Electronegtaive Atoms keep electrons less

8. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
How can you tell how well the atoms are sharing?
When the Difference in EN in the atoms bonded is less than or equal to .3
|EN1 – EN2| ≤ .3
Example: Bond between H and S
EN of H = EN of S = 2.4
|EN1 – EN2| = |2.1 – 2.4| = .3 ≤ .3
This says that H and S will share equally.

9. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
How can you tell how well the atoms are sharing?
The most equal sharing will be between atoms of the same element in a diatomic molecule such as H2.
|EN1 – EN2| ≤ .3
Example: Bond between H and S
EN of H = EN of H = 2.1
|EN1 – EN2| = |2.1 – 2.1| = 0 ≤ .3
This says there will be perfect sharing.

10. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond? .

11. COVALENT BONDING & CHEMICAL FORMULA
Electronegativity for other types of Bonds?
Other bonds exist.
They are not strictly defined but rather cover a range of EN differences as follows:
Ionic - EN difference < 1.7
Polar Covalent – from .3 to 1.7
Covalent – below .3

12. COVALENT BONDING & CHEMICAL FORMULA
Electronegativity for other types of Bonds?
Equal Sharing
Equal charge on
atoms
Unequal Sharing
Atom with higher EN becomes slightly negative
No sharing
Full charge on each
component (ion)

13. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
Why do atoms form bonds?
Atoms are more stable with full outer shells.
Atoms prefer Noble Gas arrangements of electrons
Atoms share, borrow or steal to become stable.
This is called the Octet Rule: Atoms prefer outer shells (which is usually 8 electrons.)

14. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
Hydrogen gains a full outer shell by sharing an electron with a partner atom .

15. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
With Oxygen two pair of electrons are shared, so a DOUBLE BOND is formed. The Double Bond is represented by a double dash.

16. COVALENT BONDING & CHEMICAL FORMULA
What is a Covalent Bond?
With Nitrogen three pair of electrons are shared, so a TRIPLE BOND is formed. The Triple Bond is represented by a triple dash.

17. COVALENT BONDING & CHEMICAL FORMULA
You will need to remember how to draw the Electron-dot (Lewis Structure) notation for the elements from the PT.

18. COVALENT BONDING & CHEMICAL FORMULA
You will need to remember how to draw the Electron-dot (Lewis Structure) notation for the elements from the PT.

19. COVALENT BONDING & CHEMICAL FORMULA
Electron Accounting:
5. Replace paired of electrons between atoms with dash to represent bond.
6. Check your work.
* Count electrons in structure to check the # matches # available.
* Be sure atoms have octet (except H)
Draw the Lewis Structure for CH3Br:
1. Determine the # or each atom in the molecule: C = 1, H = 3, Br = 1
2. Write the Electron Dot Notation for each atom.
3. Determine the total number of valence electrons available:
C H Br
(1) = 18 electrons
4. Arrange the atoms to form a skeleton of the molecule. If C is present, it is the central atom. If not the least EN atom is central. H is never central.

20. COVALENT BONDING & CHEMICAL FORMULA
How strong are the Bonds?
Bond strengths can be determined by the length of the bond.
The length of the bond is the distance between the atoms.
Longer bonds are weaker.
Shorter bonds are stronger.

21. COVALENT BONDING & CHEMICAL FORMULA
Covalent Bonds and Electron Configuration – When bonding occurs orbitals overlap.

22. COVALENT BONDING & CHEMICAL FORMULA
Covalent Bonds and Electron Configuration – When bonding occurs orbitals overlap.

23. COVALENT BONDING & CHEMICAL FORMULA
Covalent Bonds and Electron Configuration – When bonding occurs orbitals overlap.