1. TOPIC 4 CHEMICAL BONDING AND STRUCTURE
4.2
COVALENT BONDING

2. Covalent compounds form by the sharing of electrons.
ESSENTIAL IDEA
Covalent compounds form by the sharing of electrons.
NATURE OF SCIENCE (2.5)
Looking for trends and discrepancies – compounds containing non-metals have different properties than compounds that contain non-metals and metals.
NATURE OF SCIENCE (2.2)
Use theories to explain natural phenomena – Lewis introduced a class of compounds which share electrons. Pauling used the idea of electronegativity to explain unequal sharing of electrons. .

3. UNDERSTANDING/KEY IDEA 4.2.A
A covalent bond is formed by the electrostatic attraction between a shared pair of electrons and the positively charged nuclei.

4. ELECTRON SHARING
When atoms of 2 non-metals react together, each is seeking to gain electrons in order to achieve the stable electron configuration of a noble gas.
This tendency to form a stable arrangement of 8 electrons in the outer shell is referred to as the octet rule.
The shared pair of electrons is concentrated in the region between the 2 positively charged nuclei.
The electrostatic attraction between the 2 nuclei and the electrons constitutes the covalent bond.

5. UNDERSTANDING/KEY IDEA 4.2.B
Single, double and triple covalent bonds involve one, two and three shared pairs of electrons, respectively.

6. UNDERSTANDING/KEY IDEA 4.2.C
Bond length decreases and bond strength increases as the number of shared electrons increases.

7. BOND LENGTH AND BOND STRENGTH
Triple bonds are stronger than double bonds which are stronger than single bonds.
The strength of the bond is a measure of how much energy is required to break the bond.
Triple bonds are shorter than double bonds which are shorter than single bonds.
The number of shared electrons is greater in multiple bonds causing the electrostatic attraction to be stronger; therefore, causing the bonds to be shorter in length.
A single bond contains only one sigma bond.
A double bond contains one sigma and one pi bond.
A triple bond contains one sigma and two pi bonds.

8. UNDERSTANDING/KEY IDEA 4.2.D
Bond polarity results from the difference in electronegativities of the bonded atoms.

9. APPLICATION/SKILLS
Be able to deduce the polar nature of a covalent bond from electronegativity values.

10. COVALENT CHARACTER You can predict covalent character by two ways:
Position on the Periodic Table
Electronegativity differences
Covalent compounds tend to form between 2 non-metals.
The closer together two elements are, the more covalent.
Electronegativity
Electronegativity values are given in Table 8 of the IB Data Booklet.
Differences less than 1.8 are considered to be covalent.

11. POLARITY
A bond that is unsymmetrical with respect to electron distribution is said to be polar.
The term dipole means the bond has an area of positive charge and an area of negative charge. (delta symbol)
The Pauling scale predicts polarity by using electronegativity differences.
Values of are considered non-polar covalent.
Values between 0.4 and 1.8 are considered polar covalent.
Values greater than and equal to 1.8 are considered ionic.
Basically, the greater the electronegativity difference, the more polar the bond.

12. GUIDANCE
Bond polarity can be shown either with partial charges, dipoles or vectors.

13. GUIDANCE
Electronegativity values are given in the data booklet on page 8.

14. Aims
Aim 3: Use naming conventions to name covalently bonded compounds.

15. Diatomic Elements Gases that exist as diatomic molecules
are H2, F2, N2, O2, Cl2, Br2, I2
They are simply given their elements name.
Exist this way only when not in compounds

16. Learning Check
Use the name of the element to name the following diatomic molecules.
H2 hydrogen
N2 nitrogen
Cl2 _______________
O2 _______________
I2 _______________

17. Naming Covalent Compounds
Two nonmetals
Name each element
End the last element in -ide
Add prefixes to show more than 1 atom
Prefixes
mon hexa 6
di 2 hepta 7
tri 3 octa 8
tetra 4 nona 9
penta 5 deca 10

18. Learning check
Fill in the blanks to complete the following names of covalent compounds.
CO carbon ______oxide
CO2 carbon _______________
PCl3 phosphorus _______chloride
CCl4 carbon ________chloride
N2O _____nitrogen _____oxide

19. Dinitrogen Hexafluoride
Formula
Names
N2F6
Dinitrogen Hexafluoride
CO2
Carbon Dioxide
SiF4
Silicon Tetrafluoride
CBr4
Carbon Tetrabromide
NCl3
Nitrogen Trichloride
P2S3
Diphosphorous Trisulfide CO
Carbon Monoxide
NO2
Nitrogen Dioxide
SF2
Sulfur Difluoride
PF5
Phosphorous Pentafluoride
SO2
Sulfur Dioxide NO
Nitrogen Monoxide
CCl4
carbon tetrachloride
P2O5
diphosphorus pentoxid

20. Learning Check A. P2O5 1) phosphorus oxide 2) phosphorus pentoxide
3) diphosphorus pentoxide
B. Cl2O7 1) dichlorine heptoxide
2) dichlorine oxide
3) chlorine heptoxide
C Cl2 1) chlorine
2) dichlorine
3) dichloride

21. Citations
International Baccalaureate Organization. Chemistry Guide, First assessment Updated Brown, Catrin, and Mike Ford. Higher Level Chemistry. 2nd ed. N.p.: Pearson Baccalaureate, Print. Most of the information found in this power point comes directly from this textbook. The power point has been made to directly complement the Higher Level Chemistry textbook by Catrin and Brown and is used for direct instructional purposes only.