1. COVALENT BONDS: NONPOLAR AND POLAR

2. Covalent Bonds Definition
1) chemical bond in which two atoms share a pair
of valence electrons
2) can be a single, double, or triple bond
single, 2e-’s (-); double, 4e-’s (=); triple, 6e-’s( )
3)2 types of bonds
- polar
- non polar

3. Electrons are shared between atoms. Both elements are nonmetals
Electrons are shared between atoms. Both elements are nonmetals. Molecules are formed with covalent bonds. Two types: Polar and non-polar Covalent bonded molecules are not conductors at any state Ex: H2O, O2, CO2, C2H6, SiO2, C6H12O6
Covalent Bonds

4. Covalent Bonds

5. Bond and Lone Pairs
Valence electrons are distributed as shared or BOND PAIRS and unshared or LONE PAIRS. • •• H Cl
shared or
bond pair
lone pair (LP)
This is called a LEWIS structure.

6. Electron distribution is depicted with Lewis electron dot structures
This is how you decide how many atoms will bond covalently.
(In ionic bonds, it was decided with oxidation numbers)
G. N. Lewis

7. Nonpolar Covalent Molecules

8. Nonpolar Covalent Molecules
Equal distribution of charge around a central atom.
Molecule has a symmetrical shape
Nonpolar Covalent Molecules

9. THEY BOTH GET FULL OUTER SHELLS (AN OCTET)
In a chlorine molecule, each of the atoms shares a pair of electrons circled in GREEN, making the covalent bond. Since it’s just one pair being shared, this is a SINGLE COVALENT BOND.
Each of the chlorine atoms also has three pairs each of UNSHARED ELECTRONS.
THEY BOTH GET FULL OUTER SHELLS (AN OCTET)
BY SHARING.

10. unshared electrons
When electrons are written as a Lewis diagrams, they are usually paired. Electrons prefer being in pairs. When electrons are shared between atoms, one electron from each atom connects together, making a SINGLE BOND.
Electrons not involved in bonding are mostly paired away from the bond. They are the “unshared” electrons.
If they connect 2 or 3 pairs at a time, they make DOUBLE or TRIPLE BONDS.

11. When 2 oxygen atoms combine to form a molecule, each keeps two pairs of unshared electrons, but shares two pairs (in the middle) with each other.
That is a DOUBLE COVALENT BOND

12. and each atom also has one pair of UNSHARED ELECTRONS.
Diatomic Nitrogen makes a TRIPLE COVALENT BOND
and each atom also has one pair of UNSHARED ELECTRONS.

13. Double and even triple bonds are commonly observed for C, N, P, O, and S
H2CO
SO3
C2F4

14. Chlorine
forms a
covalent
bond
with
itself
Cl2

15. How
will
two
chlorine
atoms
react? Cl Cl

16. Cl Cl Each chlorine atom wants to gain one electron to achieve a
full outer shell.

17. Cl Cl do to achieve an octet? Neither atom will give up an electron -
chlorine is highly electronegative.
What’s the solution – what can they
do to achieve an octet?

18. Cl Cl

19. Cl Cl

20. Cl Cl

21. Cl Cl

22. Cl Cl
Full (octet)

23. Cl Cl
Full (octet)
We circle the shared electrons

24. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle
We circle the shared electrons

25. Cl Cl Full shells are achieved by each atom sharing the
electron pair in the middle

26. Cl Cl This is the bonding pair circle the electrons for
each atom that completes
their octets

27. Cl Cl It is a single bonding pair circle the electrons for
each atom that completes
their octets

28. Cl Cl It is called a SINGLE BOND circle the electrons for
each atom that completes
their octets

29. Single bonds are abbreviatedCl Cl
Single bonds are abbreviated
with a dash

30. This is the chlorine molecule,Cl Cl
This is the chlorine molecule,
Cl2

31. O2
Oxygen is also one of the
diatomic molecules

32. O
How will two oxygen atoms bond?

33. O
Each atom has
two unpaired electrons

34. O

35. O

36. O

37. O

38. O

39. O

40. O Oxygen atoms are highly electronegative, so both atoms
want to gain two electrons.

41. O

42. O

43. O O

44. O O

45. O O

46. Both electron pairs are shared.

47. O O
6 valence electrons
plus 2 shared electrons
= full shell (octet)

48. O O
6 valence electrons
plus 2 shared electrons
= full shell (octet)

49. O O
two bonding pairs,
making a double bond

50. O O =
For convenience, the double bond
can be shown as two dashes.

51. O =
this is so cool!!
This is the
oxygen molecule, O2

52. Polyatomic ions are composed of two or
more atoms, held together by covalent
bonds.
Polyatomic ions act as a unit in bonding.
Bicarbonate ion Phosphate ion
Charge is -1. Charge is -1.

53. Covalent Bonds Can be polar or nonpolar Non Polar
bonded atoms that share e-’s equally
true when same atoms bonded
ex. Cl – Cl: Cl2
Polar
bonded atoms that do not share e-’s equally
different atoms bonded, depends on shape, too H
ex: NH3 H – N – H

54. Polar Bonds
HCl is POLAR because it has a positive end and a negative end. (difference in electronegativity)
Cl has a greater share of the bonding electron’s time than does H
Cl end has slight negative charge and H end has slight positive charge.

55. Polar Bonds
This is why oil and water will not mix! Oil is nonpolar, and water is polar.
The two will repel each other, and so
you can not
dissolve one
in the other

56. Polar Bonds “Like Dissolves Like” Polar dissolves Polar
Nonpolar dissolves Nonpolar

57. Polar Covalent Molecules

58. polar compounds
Formed when 2 atoms with different electro-negativities form a covalent bond.
The atoms DO NOT SHARE electrons equally.
The electrons are more strongly attracted to the MOST electronegative atom.
Molecules are asymmetrical.

59. Water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

60. MOLECULAR POLARITY
A molecule can also be polar, if the electrons are moved about by polar bonds giving the WHOLE MOLECULE a positive and a negative side.
The opposite sides of polarity are called dipoles, which means 2 poles, one positive and the other end negative.
The oxygen side is negative since it takes the electrons, the hydrogen side is more positive because it lost the electrons.

61. Naming Covalent Compounds

62. Naming Covalent Compounds Cont.
Rules for the prefix system
1. Less electronegative (leftmost) element is given first.
It is given a prefix only if there’s more than one atom in the molecule.
2. The second element gets the ide ending and a prefix indicating the number of atoms contributed
ex. Monoxide or pentoxide

63. Covalent Naming of 2 Nonmetals
To name compounds of different elements:
Name the first element
Change the last element’s last syllable to –ide
Add prefixes:
mon/mono 1 hexa 6
di hepta 7
tri octa 8
tetra 4 nona 9
penta 5 deca 10
Covalent Naming of 2 Nonmetals

64. Fill in the blanks to complete the following names of covalent compounds.
CO carbon ______oxide
SiO2 silicon ______oxide
PCl3 phosphorus _______chloride
CCl4 carbon ________chloride
N2O _____nitrogen ___oxide
P2O5 ___phosphorus ____oxide
Learning Check

65. Solution CO carbon monoxide CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen monoxide
P2O5 diphosphorus pentoxide
Solution