1. Chapter 7 & 8 Chemical Bonding
This week we will learn:
Valence electrons
Lewis dot structures
Octet Rule
Electronegativity (review)
Cations and Anions (review)
What are Chemical Bonds?
Different Types of Chemical Bonds
Chemistry _ Notes
Dr. Chirie Sumanasekera
11/13/ 2017

2. Today: we will learn: What are Valence electrons?
Review Electron configurations
How to find Valence electrons for any given element
Chemistry _ Notes
Dr. Chirie Sumanasekera
11/13/ 2017

3. 1. Valence electrons:
Valence electrons = The electrons in the outermost Principal Energy level of an atom.
Like the front lines of soldiers in an ARMY who encounter the enemy directly!
Valence electrons are shared or transferred during chemical reactions
The number of valence electrons are directly responsible for the chemical properties and reactivity of elements
Each group in the periodic table is arranged based on the Valence electron numbers
Li atom: 1S2 2S1
Valence shell Electron
n = 1
n = 2
Nucleus
Inner shell (shields valence shell from attraction of nucleus
Valence shell

4. Segment of an electron configuration
Number of total electrons
Li : 1S2 2S1
Sub-Level (has orbitals)
Principal Energy Level (n=2)

5. Valence electrons (V. E.) and group numbers1 2 3 4 5 6 7 9 8
Periodic table of Elements 10 1
Each group in the periodic table is arranged based on the Valence electron numbers:
Group1 has 1 V.E., Group 2 has 2 V.E. , group 3 has 3 V.E. and so on till group 10. Group 10 has 10 V.E.
Groups , we start counting V.E. from 1 to 8 again. See figure above.

6. Chapter 7 and 8 Today we will learn:
What are Lewis (Electron) dot diagrams?
Finding Noble gas valance electrons
What is the Octet rule
Chemistry _ Notes
Dr. Chirie Sumanasekera
11/14/ 2017

7. 2. Electron (Lewis) dot structures
Lewis structures [also known as Lewis dot diagrams, Lewis dot formulas (structures), and electron dot structures]:
Are diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons
In the case of an atom, the structures show valance electrons
Ex: Nitrogen (N) has 5 valance electrons: N N
Place the valance electrons, one at a time, on the line clock-wise from the TOP N N N
Pair the remaining valance electrons, one at a time, on the line clock-wise from the TOP

8. Determining the number of valence electrons in a given element
Atomic number
Element
Electron configuration
# of Valence Electrons
Electron dot diagram 1 H
1s1 2 He
1s2 3 Li
1s2 2s1 4 Be
1s2 2s2 5 B
1s2 2s2 2P1 6 C
1s2 2s2 2P2 7 N
1s2 2s2 2P3 8 O
1s2 2s2 2P4 9 F
1s2 2s2 2P5 10 Ne
1s2 2s2 2P6 11 Na
1s2 2s2 2P6 3s1 12 Mg
1s2 1s2 2P2 3s2
Period-1
Energy level: n=1
Sub-levels: s H
Period-2
Energy level: n=2
Sub-levels: s,p C Ne
Period-3
Energy level: n=3
Sub-levels: s,p,d

9. Number of valence electrons in Noble Gases
Atomic number
Element
Electron configuration
# of V.E. 10 Ne
1s2 2s2 2p6 18 Ar
1s2 2s2 2p6 3s2 3p6 36 Kr 54 Xe 86 Rn

10. Number of valence electrons in Noble Gases
Atomic number
Element
Electron configuration
# of V.E. 10 Ne
1s2 2s2 2p6 8 18 Ar
1s2 2s2 2p6 3s2 3p6 36 Kr
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 54 Xe
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 86 Rn
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6
All noble gases have 8 valance electrons as their highest Principal Energy Level-SUB LEVELS (S and P) are completely filled with electrons. This is the reason for the Non-reactivity and stability of noble gases.

11. - 1e = [Ne] electron configuration
2. Octet Rule
Octet rule: Atoms are always trying to get 8 electrons in their outer shell (principal energy level) to be like the nearest noble gas in the periodic table. This is because, having 8 electrons in outer shell is energetically very stable.
N = 5e
Cl = 7e
Na = 1e
Mg = 2e
C = 4e
Valence Electrons
- 1e = [Ne] electron configuration
According to octet rule
- 2e = [Ne] electron configuration
+ 4e = [Ne] electron configuration
+ 3e = [Ne] electron configuration
+ 1e = [Ar] electron configuration

12. Chapter 7 and 8: CHEMICAL BONDS Today:
we will learn:
Review electronegativity
Review Cations and anions
What are chemical bonds?
Types of chemical bonds
Chemistry _ Notes
Dr. Chirie Sumanasekera
11/17/ 2017

13. 1. Electronegativity (Review of ch-6)
Electronegativity tends to increase in the periodic table:
F = most electronegative
Fr = least electronegative

14. 2. Cations and anions (Review of ch-6)
Tend to form CATions (+) by giving electrons to complete octet
Tend to form ANions (-) taking electrons to complete octet
Left side of table
Right side of table (excluding noble gases)
Periodic table

15. 3. What are Chemical bonds?
To make molecules or compounds, atoms must “stick” together.
This “sticking-together” happens because of chemical BONDS.
CHEMICAL BONDS:
Between ATOMS (intra-molecular bonds= inside molecules = atoms)
Between MOLECULES (inter-molecular bonds)
3 TYPES of BONDS between ATOMS:
Covalent Bonds (sharing electrons between atoms)
Ionic bonds (transferring electrons between atoms)
Metallic bonds (atoms collectively sharing a sea of electrons)

16. Electronegativity (Review)

17. Electronegativity (Review)

18. - 1e = [Ne] electron configuration
2. Octet Rule
Octet rule: Atoms are always trying to get 8 electrons in their outer shell (principal energy level) to be like the nearest noble gas in the periodic table. This is because, having 8 electrons in outer shell is energetically very stable.
N = 5e
Cl = 7e
Na = 1e
Mg = 2e
C = 4e
Valence Electrons
- 1e = [Ne] electron configuration
According to octet rule
- 2e = [Ne] electron configuration
+ 4e = [Ne] electron configuration
+ 3e = [Ne] electron configuration
+ 1e = [Ar] electron configuration