1. Chemical
Bonding

2. electrons in the outermost principal energy level
valence electrons –
electrons in the outermost principal energy level
Example:
Oxygen has 6 valence electrons since its electron configuration is 1s2 2s2 2p4
6 electrons
Inner shell
Outer shell

3. 8
Octet Rule
Atoms tend to form an octet of electrons in the valence shell by gaining, losing or sharing electrons.
Example:
Oxygen has 6 valence electrons
1s2 2s2 2p4
Oxygen atoms have a tendency to gain 2 electrons to achieve an octet (8).

4. Na + Cl a Na+[ Cl ]- H + Cl a H Cl
When chlorine reacts with sodium it forms an ionic bond.
Na Cl
a Na+[ Cl ]-
Ionic Bond
Yet, when chlorine reacts with hydrogen, it forms a covalent bond.
H Cl
a H Cl
Covalent Bond

5. How are you supposed to know whether a compound like HCl or NaCl is ionic or covalently bonded?

6. An ionic bond will form only if one of the atoms has a much greater attraction of electrons than the other atom.
What measures electron attraction is electronegativity.

7. Table of Electronegativities (pg 151)
Increases

8. Electronegativity difference
To form an ionic bond, the element must be 1.7 or more than the other element.
Na + Cl
Electronegativities:
Ionic Bond
2.1
Electronegativity difference

9. Electronegativity difference
To form a covalent bond, the difference between the two elements must be less than 1.7
H + Cl
Electronegativities:
Covalent Bond
0.9
Electronegativity difference

10. H Cl Needs 2 electrons Has 2 electrons Has 8 electrons
Covalent bond – is the sharing of valence electrons between two atoms.

11. HCl d+ d- 2.1 3.0 0.9 Polar Covalent bond
Polar Covalent bond
This bond is considered to be covalent with slight ionic character because of the slight positive and negative charges at each end.

12. H H By sharing each others electrons, each atom now has 2 electrons.
Not stable with one electron

13. Nonpolar Covalent bondH
Electronegativities:
0.0
Electronegativity difference
Nonpolar Covalent bond

14. H H Cl Na+[ Cl ]- d- d+ Ionic Bond- attraction between ions
Polar Covalent Bond- the unequal sharing of electrons
H Cl d- d+
Nonpolar Covalent Bond- the equal sharing of electrons H

15. Electronegativity difference
Bond type
Electronegativity difference
Ionic
1.7 or more
Polar Covalent
0.3 to 1.6
Nonpolar Covalent
0.0 to 0.2

16. In each pair, which will be more negative?
Examples from you textbook pg 163
Classify each of the following pairs as ionic, polar covalent or nonpolar covalent.
In each pair, which will be more negative?
H and S
Cs and S
Cl and S

17. Electronegativity difference
Classify each of the following pairs as ionic, polar covalent or nonpolar covalent. In each pair, which will be more negative?
Electronegativity difference
More negative atom
Bond type
polar covalent
H and S
sulfur
2.5 – 2.1 = 0.4
Cs and S
sulfur
2.5 – 0.7 = 1.8
ionic
polar covalent
Cl and S
3.0 – 2.5 = 0.5
chlorine

18. In each pair, which will be more negative?
Examples from you textbook pg 163
Classify each of the following pairs as ionic, polar covalent or nonpolar covalent.
In each pair, which will be more negative?
Cl and Ca
Cl and O
Cl and Br

19. Electronegativity difference
Classify each of the following pairs as ionic, polar covalent or nonpolar covalent. In each pair, which will be more negative?
Electronegativity difference
More negative atom
Bond type
Cl and Ca
ionic
3.0 – 1.0 = 2.0
chlorine
polar covalent
Cl and O
3.5 – 3.0 = 0.5
oxygen
nonpolar covalent
Cl and Br
3.0 – 2.8 = 0.2
chlorine

20. Given the formula of a molecular compound or polyatomic ion, you’ll be asked to show how it’s put together. This is done by drawing the Electron Dot Structure (or Lewis Structure).
Wasn’t that easy?
For example, H2O
The oxygen achieves an octet. H H O
This is the structure for the water molecule.
Both hydrogens achieve a duet?
It’s formula is H2O, but its structure is more like HOH.