1. Demo Salt Crystal (hanging on ceiling)
Covalent Compounds
Demo Salt Crystal (hanging on ceiling)
Videodisk Unit 3

2. Covalent Bonding Takes place between two non-metals
Electrons are shared by both nuclei to help each attain 8 valence electrons
There are several electrostatic interactions in these bonds:
Attractions between electrons and nuclei
Repulsions between electrons
Repulsions between nuclei
A molecule is formed when two or more atoms bond covalently
Covalent Bond Video (25 sec)
Ionic and Covalent (2 min)

3. Properties of Covalent Compounds
Drawing the Lewis Dot Diagram of a molecule helps determine the specific properties.
Properties of Covalent Compounds
Most have low melting points and low boiling points.
Many are liquids and gases at room temperature.
Nonconductors of electricity. AKA Nonelectrolytes

4. NH3 H H N H Lewis Dot Diagram Steps
1. Add up the number of valence electrons on each atom in the molecule:
= 8
2. Draw the central atom and use sticks (two electrons) to connect the terminal atoms to the central.
3. Be certain all atoms other than hydrogen have an octet. Use lone pairs on central if necessary.
4. Make double bonds if there are not enough electrons left for the central atom’s octet.
NH3 H H N H
Hydrogen only needs two electrons to fill its outer shell.
Everyone else needs eight electrons in their outer shell.

5. Draw dot diagrams for the following: CH4 N2
PCl CO2
SH O2
BH3 H
H-C-H
H-S H .. :
H-B-H H

6. Exceptions to the Octet Rule
The Lewis structure that deals with boron (B):
boron shares 3 electrons to form three single bonds
The Lewis structures of SF6 and PCl5 (for elements in Period 3 or greater) 6

7. Comparing length and strength of single, double and triple bonds
Use a model kit to construct these three molecules.
How are the distances between the carbon atoms different?

8. Relative lengths:
single bond ˃ double bond ˃ triple bond
Relative strengths:
triple bond ˃ double bond ˃ single bond

9. Dinitrogen Pentaoxide
Naming Covalent Bonds
Write names of both elements
Add -ide to the last name
Add prefixes at beginning of each word to indicate how many of each element.
Exception- do not use mono in front of the first element
N2O5
Dinitrogen Pentaoxide

10. Covalent Bonding Prefixes
(mono-)
di-
tri-
tetra-
penta-
hexa-
hepta-
octa-
nona-
deca-

11. Practice Naming Name the following: CCl4 PCl3 SH2 CO NO3 N2O4
Carbon tetrachloride
Phosphorus trichloride
Sulfur dihydride
Carbon monoxide
Nitrogen trioxide
Dinitrogen tetraoxide

12. Molecular Elements H2 N2 O2 F2 Common Covalent Compounds Cl2 Br2 I2
Certain elements occur as 2 atom molecules
Rule of 7’s
there are 7 common diatomic elements
find the element with atomic number 7, N
make a figure 7 by going over to Group 7A, then down
don’t forget to include H2
VIIA 7 H2
N2 O F2
Common Covalent Compounds
Cl2
Br2
H2O Water
NH3 Ammonia
CH4 Methane I2

13. Acid Nomenclature

14. How to identify an acid:
The formula of an acid starts with “H”
HCl hydrochloric acid
HNO3 nitric acid
H3PO4 phosphoric acid

15. 1. Binary Acids (Two elements, one of which is hydrogen) HCl HBr H2S
Two types of acids:
1. Binary Acids (Two elements, one of which is hydrogen) HCl HBr H2S
2. Oxyacids (contain oxygen, usually a polyatomic ion bonded to hydrogen) H2SO4 HClO3 HClO4

16. If it is a binary acid:
Prefix = Hydro- root = second element’s name Suffix = -ic acid HCl = hydro- chlor -ic acid→ hydrochloric acid HBr= hydro- brom -ic acid →hydrobromic acid H2S = hydro – sulfur – ic acid →hydrosulfuric acid

17. If it is an oxyacid Prefix = none root = anion (polyatomic name)
Suffix =depends! + acid
If anion ends in –ate replace with –ic acid
If anion ends in –ite replace with –ous acid
Example: HNO₃ Example: HNO₂
Since NO₃⁻ = Nitrate Since NO₂⁻ = Nitrite
HNO₃ = Nitric Acid HNO₂ = Nitrous acid
*Sulfate/ite root goes to sulfur (sulfuric and sulfurous acid). Same is true for phosphate

18. Examples
HNO2
H2SO3
H3PO4
HNO3
HCl
H2SO4

19. Examples- answers nitrous acid sulfurous acid phosphoric acid
nitric acid
hydrochloric acid
sulfuric acid

20. Try on your own 1. HCl 2. HBr 3. H₂SO₄ 4. H₂S 5. H₂CO₃ 6. HC₂H₃O₂
7. H₃PO₄
8. H₃P
9. H₂CrO₄
10. H₂Cr

21. Answers 1. HCl- hydrochloric acid 2. HBr- hydrobromic acid
3. H₂SO₄- sulfuric acid
4. H₂S- hydrosulfuric acid
5. H₂CO₃- carbonic acid
6. HC₂H₃O₂- acetic acid
7. H₃PO₄- phosphoric acid
8. H₃P- hydrophosphoric acid
9. H₂CrO₄- chromic acid
10. H₂Cr- hydrochromic acid

22. Try writing the formulas:
Sulfuric acid
Nitric acid
Hydrochloric acid
Acetic acid
Hydrofluoric acid
Phosphorous acid
Carbonic acid
Nitrous acid
Phosphoric acid
Hydrosulfuric acid

23. Answers
H₂SO₄
HNO₃
HCl
HC2H3O2 HF
H₃PO₃
H₂CO₃
HNO₂
H₃PO₄
H₂S