1. Chapter 5 Chemical Bonding
The Covalent Bond

2. Covalent or Ionic ???
Electronegativity – the attraction that an atom has for the electrons that it is sharing w/ another atom
Scale devised by Nobel Prize winner Linus Pauling
Based on scale with fluorine assigned 4.0, the highest value
Material from karentimberlake.com and
H. Stephen Stoker

3. Forming Chemical Bonds
According to the Lewis model
an atom may lose or gain enough electrons to acquire a filled valence shell and become an ion. An ionic bond is the result of the force of attraction between a cation and an anion.
an atom may share electrons with one or more other atoms to acquire a filled valence shell. A covalent bond is the result of the force of attraction between two atoms that share one or more pairs of electrons.
Material from karentimberlake.com and
H. Stephen Stoker

4. Covalent Bonds
A chemical bond in which 2 atoms share a single of electron to form one bond
Examples F and H
Material from karentimberlake.com and
H. Stephen Stoker

5. Covalent Bonds H + H H : H = HH = H2 hydrogen molecule
Two nonmetal atoms form a covalent bond because they have less energy after they bonded
H H H : H = HH = H2
hydrogen molecule
Material from karentimberlake.com and
H. Stephen Stoker

6. Double Covalent Bond 2 pairs of electrons are shared between 2 atoms
Example O2
       
 O   O   O::O
double bond
Material from karentimberlake.com and
H. Stephen Stoker

7. Triple Covalent Bond 3 pairs of electrons are shared between 2 atoms
Example N2
       
 N   N   N:::N
 
triple bond
Material from karentimberlake.com and
H. Stephen Stoker

8. Diatomic Elements
Elements that are naturally in molecules with 2 atoms each.
HONClBrIF (pneumonic)
Existing as diatomic molecule yields a stable octet
Gases that exist as diatomic molecules are H2, F2, N2, O2, Cl2, Br2, I2
Examples Fluorine & Bromine
Material from karentimberlake.com and
H. Stephen Stoker

9. Learning Check
Use the name of the element to name the following diatomic molecules.
H2 hydrogen
N2 nitrogen
Cl2 _______________
O2 _______________
I2 _______________
Material from karentimberlake.com and
H. Stephen Stoker

10. Solution
Use the name of the element to name the following diatomic molecules.
H2 hydrogen
N2 nitrogen
Cl2 chlorine
O2 oxygen
I2 iodine
Material from karentimberlake.com and
H. Stephen Stoker

11. Lewis Structures Other molecules having single covalent bonds H2O
The hydrogens share their electrons w/ oxygen so that O has 8 e- and each H has 2 e-
Material from karentimberlake.com and
H. Stephen Stoker

12. Covalent Bonds in NH3 Bonding pairs H   H : N : H
Lone pair of electrons
(unshared pair)
Material from karentimberlake.com and
H. Stephen Stoker

13. Drawing Lewis Structures
1. Determine the number of valence electrons in the molecule
2. Decide on the arrangement of atoms in the molecule
3. Connect the atoms by single bonds
4. Show bonding electrons as a single line; show nonbonding electrons as a pair of Lewis dots
5. In a single bond, atoms share one pair of electrons; in a double bond, they share two pairs, and in a triple bond they share three pairs.
Material from karentimberlake.com and
H. Stephen Stoker

14. Coordinate Covalent Bond
Bond in which only one atom donates electrons to form the bond
Sometimes an arrow is used to designate the coordinate covalent bond
Material from karentimberlake.com and
H. Stephen Stoker

15. Chemical Bonding: The Covalent Bond Model cont’d
Material from karentimberlake.com and
H. Stephen Stoker

16. Chemical Bonding: The Covalent Bond Model cont’d
Fig. 5.10
Linus Pauling received the Nobel Prize in chemistry in 1954 for his work on the nature of the chemical bond.
© Bettman/CORBIS
Material from karentimberlake.com and
H. Stephen Stoker

17. Electronegativity
The attraction of an atom for electrons is called its electronegativity.
Fluorine has the greatest electronegativity.
The metals have low electronegativities.
Material from karentimberlake.com and
H. Stephen Stoker

18. Chemical Bonding: The Covalent Bond Model cont’d
Fig. 5.11
Abbreviated periodic table showing Pauling electronegativity values for selected representative elements.
Material from karentimberlake.com and
H. Stephen Stoker

19. Electronegativity
Electronegativity: a measure an atom’s attraction for the electrons it shares in a chemical bond with another atom
on the Pauling scale, fluorine, the most electronegative element is assigned a value of 4.0, and all other elements are assigned values relative to fluorine
Material from karentimberlake.com and
H. Stephen Stoker

20. Bond Polarity: Nonpolar
Nonpolar covalent bond
Electrons are shared between atoms with the same electronegativity values.
Difference = 0
Examples:
N Br2
Material from karentimberlake.com and
H. Stephen Stoker

21. Bond Polarity: Polar Polar covalent bond
Electrons are shared between different nonmetal atoms Examples:
O-Cl O-S N-Cl
Material from karentimberlake.com and
H. Stephen Stoker

22. Chemical Bonding: The Covalent Bond Model
Fig. 5.12
(a) In the nonpolar covalent bond present, there is a symmetrical distribution of electron density. (b) In the polar covalent bond present, electron density is displaced because of its electronegativity.
Material from karentimberlake.com and
H. Stephen Stoker

23. Chemical Bonding: The Covalent Bond Model
Material from karentimberlake.com and
H. Stephen Stoker

24. Learning Check Identify the type of bond between the following atoms
A. K-N
1) nonpolar ) polar 3) ionic
B. N-O
1) nonpolar 2) polar 3) ionic
C. Cl-Cl
1) nonpolar 2) polar 3) ionic
Material from karentimberlake.com and
H. Stephen Stoker

25. Solution A. K-N 3) ionic B. N-O 2) polar, covalent
C. Cl-Cl 1) nonpolar, covalent
Material from karentimberlake.com and
H. Stephen Stoker

26. Covalent or Ionic ???
To decide whether a bond is covalent or ionic find the difference in electronegativities
< 2.0 covalent
> 2.0 ionic
Try KF, MgS, Cl2
Material from karentimberlake.com and
H. Stephen Stoker

27. Character of Bonds
Chemist find it better to express chemical bonds as % ionic and % covalent
Relates electronegativity to ionic and covalent percentages
Table 7.2 (p 159) in text
Try KF, MgS, Cl2
Material from karentimberlake.com and
H. Stephen Stoker

28. Molecular Polarity Just like bonds molecules can have polarity Look at
Molecule geometry atoms (how atoms are arranged in space)
Bond polarity
Material from karentimberlake.com and
H. Stephen Stoker

29. Chemical Bonding: The Covalent Bond Model
Fig. 5.13
(a) Methane is a nonpolar tetrahedral molecule. (b) Methyl chloride is a polar tetrahedral molecule.
Material from karentimberlake.com and
H. Stephen Stoker

30. Electronegativity Material from karentimberlake.com and
H. Stephen Stoker

31. Writing Formulas Nonmetal/Nonmetal
In covalent bonds, the element with the lowest electronegativity is written first
Material from karentimberlake.com and
H. Stephen Stoker

32. Chemical Bonding: The Covalent Bond Model
Table 5.1
Material from karentimberlake.com and
H. Stephen Stoker

33. Chemical Bonding: The Covalent Bond Model
Table 5.2
Material from karentimberlake.com and
H. Stephen Stoker

34. Naming of 2 Nonmetals Name each element End the last element in –ide
Add prefixes to show more than 1 atom
Prefixes
mon 1 hexa 6
di 2 hepta 7
tri 3 octa 8
tetra 4 nona 9
pent 5 deca 10
Material from karentimberlake.com and
H. Stephen Stoker

35. 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
Material from karentimberlake.com and
H. Stephen Stoker
© Karen Timberlake

36. Solution CO carbon monoxide CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen monoxide
Material from karentimberlake.com and
H. Stephen Stoker
© Karen Timberlake

37. Learning Check P2O5 Cl2O7 Cl2 Material from karentimberlake.com and
H. Stephen Stoker

38. Solution A. P2O5 diphosphorus pentoxide B. Cl2O7 dichlorine heptoxide
C Cl2 chlorine
Material from karentimberlake.com and
H. Stephen Stoker
© Karen Timberlake

39. Learning Check Examples
draw a Lewis structure for hydrogen peroxide, H2O2
draw a Lewis structure for methanol, CH3OH
draw a Lewis structure for acetic acid, CH3COOH
Material from karentimberlake.com and
H. Stephen Stoker

40. Lewis Structures Material from karentimberlake.com and
H. Stephen Stoker

41. 3-D Characteristics of Molecules
Atoms and molecules have 3 dimensions
Shapes of molecules lead to additional properties of covalent compounds
Polar covalent Bonding
When electrons are not shared equally between two atoms
Bond that is certain % ionic
Nonpolar covalent Bonding
Electrons are shared equally
Diatomic atoms
Material from karentimberlake.com and
H. Stephen Stoker

42. More Electron Pairs Electron Angle Bonded Name of Pairs Atoms Shape
4 109° tetrahedral
4 109° pyramidal
4 109° bent, angular
Material from karentimberlake.com and
H. Stephen Stoker

43. Shapes of Molecules Number of electron pairs 2
(= negative charge clouds)
Number of bonded atoms
Angle °
Name of shape linear
Material from karentimberlake.com and
H. Stephen Stoker

44. Electron Shape with 3 Pairs
Material from karentimberlake.com and
H. Stephen Stoker

45. SO2 :O:: S:O: S S has 2 bonded atoms , 1 lone pair (electron cloud)
120°, angular
:O:: S:O: S ..
O O
Material from karentimberlake.com and
H. Stephen Stoker