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. Polar and Non-polar Covalent Bonds
Though atoms often form compounds by sharing electrons, the electrons are not always shared equally.
If the electrons are shared equally it is a non-polar covalent bond
If the electrons are not shared equally it is a polar covalent bond

4. Properties of Covalent Compounds
Most have low melting points and low boiling points.
Many are liquids and gases at room temperature.
Polar covalent molecules dissolve in water.
Nonconductors of electricity.

5. Lewis Structures
Using an atoms dot diagram we can predict how different atoms will bond covalently to form molecules
Each bond between atoms requires each atom to share one electron with the other atom.
Example:
F F
F - F

6. NH3 H N H H H N H H Dot Diagram Steps
1. Draw out atoms with valence electrons (dot structures)
2. Connect 2 e- to share until all atoms have full shells
3. Redraw with connected electrons as the bond
4. Redraw any lone pairs of electrons not involved with bonding
NH3 H N H H
Hydrogen only needs two electrons to fill its outer shell.
Everyone else needs eight electrons in their outer shell. H N H H

7. Double and Triple bonds
Sometimes more than one pair of electrons are shared to meet the octet rule
Double Bonds= 2 pairs of electrons shared between two atoms
Triple Bonds= 3 pairs of electrons shared between two atoms

8. Covalent Lewis Structures: Multiple Bonds
When two electron pairs are shared between two atoms, the resulting bond is a double bond.
these bonds are shorter and stronger than single bonds
Consider oxygen gas: 8

9. Covalent Lewis Structures: Multiple Bonds
When three electron pairs are shared between two atoms, the resulting bond is a triple bond
these bonds are shorter and stronger than double or single bonds
Consider nitrogen gas: 9

10. Some Clues for Drawing Dot Diagrams
Put the single atom in the middle of the dot diagram (the one that will have the most bonds)
Hydrogen is never in the middle of the dot diagram H
When redrawing, we use dashes to represent 2 shared electrons Remember to redraw the nonbonding electrons
Resonance means there are many possibilities and all are present. (Example: SO3) N H H

11. Practice Drawing Draw dot diagrams for the following: CH4 PCl3 SH2
COH2 H
H-C-H ..
H-S H : .. :
O=C-H H

12. Exceptions to the Octet Rule
The Lewis structure for NO (having odd number
of electrons)
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) 12

13. Lewis Structures B C N O F some common bonding patterns
C = 4 bonds & 0 lone pairs
Different bonding combinations:
4 single bonds
2 double bonds
1 single + 1 triple bond
2 single + 1 double bond
N = 3 bonds & 1 lone pair
O = 2 bonds & 2 lone pairs
H and halogen = 1 bond
B = 3 bonds & 0 lone pairs B C N O F 13

14. 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

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

16. Practice Naming Name the following: CCl4 PCl3 SH2 CO2 NO3
Carbon tetrachloride
Phosphorus trichloride
Sulfur dihydride
Carbon dioxide
Nitrogen trioxide

17. Common Covalent Compounds
Diatomic Elements
elements that always occur in pairs
name these using the element name
Common Covalent Compounds
H2O Water
NH3 Ammonia
CH4 Methane

18. Acid Nomenclature

19. How to identify an acid:
The formula of an acid starts with “H” (for now)
HCl
hydrochloric acid

20. How to identify an acid:
The formula of an acid starts with “H” (for now)
HNO3
nitric acid

21. How to identify an acid:
The formula of an acid starts with “H” (for now)
H3PO4
phosphoric acid

22. 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

23. 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

24. 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

25. Examples
HNO2
H2SO3
H3PO4
HNO3
HCl
H2SO4

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

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

28. 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

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

30. Answers
H₂SO₄
HNO₃
HCl
CH₃COOH HF
H₃PO₃
H₂CO₃
HNO₂
H₃PO₄
H₂S