1. Aim: What are covalent bonds and how are they formed?
Do Now: explain in terms of electronegativity why you think in covalent bonding there is a sharing of electrons and not a transfer of electrons

2. Why do atoms form chemical bonds?
Atoms form chemical bonds between each other to become more stable.
Ionic bonds- bond formed by the transfer of valence electrons
Covalent bonds –bonds formed through the sharing of valence electrons

3. Chemical Bonds and Energy
A chemical bond has stored energy
When a bond is broken energy is absorbed (taken in); energy is needed to break the bond
When a bond is formed, energy is released, and the compounds formed have lower energy

4. Energy and Bonding
Na + Cl  NaCl Bond is formed, energy is released N2  N + N Bond is broken, energy is absorbed
copy

5. Molecular Compounds
The atoms in molecular compounds are held together by covalent bonds
Covalent bonds are the sharing of electrons between nonmetal atoms.
The electrons of one atom are attracted to the protons in the nucleus of the second atoms, and vice versa.

6. Molecule
A molecule is a neutral group of atoms joined together by covalent bonds
Diatomic molecules- two atoms covalently bonded to each other
Examples of molecules of elements: H2, O2, N2, Cl2, Br2, I2, F2
Example of molecule of compound: HCl

7. Covalent Bond vs Ionic Bond

8. In pairs:
Come up with an analogy and write it down describing ionic bonding and covalent bonding.
Examples of analogies:
Bacterial chromosomes are like spaghetti.
Blood vessels are like highways.

9. Properties of Molecular Compounds
Mostly liquid or gases at room temperature
Lower melting points than ionic compounds (meaning the bonds are weaker than ionic bonds)

10. Ionic vs. Covalent IONIC COVALENT Bonded Name Salt Molecule
Bonding Type
Transfer e-
Share e-
Types of Elements
Metal & Nonmetal
Nonmetals
Physical State
Solid
Solid, Liquid, or Gas
Melting Point
High (above 300ºC)
(strong bond)
Low (below 300 ºC)
(weaker bond)
Solubility
Dissolves in Water
Varies
Conductivity
Good in liquid phase
Poor

11. Summary
tool/plix.html?eId=SCI.CHE.404&questionId=54402a515aa41377f01caf54&a rtifactID= &conceptCollectionHandle=chemistry-::-covalent- bond&collectionCreatorID=3&backUrl=https%3A// try/covalent- bond/%3Fdifficulty%3Dall%26by%3Dck12%23interactive&plix_redirect=1

12. Practice: True or False
All molecular compounds are composed of atoms of two or more elements.
All compounds are molecules.
Molecular compounds are composed of two or more nonmetals.
Atoms in molecular compounds exchange electrons.
Molecular compounds have higher melting and boiling points than ionic compounds.

13. Structural Formula
A structural formula is a formula that shows the arrangement of atoms in the molecule of a compound.
Copy

14. Octet Rule in Covalent Bonding
In covalent bonding, atoms usually acquire a total of eight electrons, or an octet, by sharing electrons.
The shared electrons of a covalent bond is either shown by one, two, or three lines
Copy

15. How can you tell how many bonds an atom can form?
The number of unpaired valence electrons determines how many bonds an atom can form.
Determine how many bonds each of the following atoms can form
Hydrogen
Carbon
Nitrogen
Oxygen
Fluorine

16. Shared versus Unshared Electrons
A Shared Pair is a pair of valence electrons that is shared between atoms
An Unshared Pair is a pair of valence electrons that is not shared between atoms
Copy

17. Single Covalent Bond
A Single Covalent Bond consists of two atoms held together by sharing 1 pair of electrons (2 e-)
Copy

18. Electron Dot Structure

19. Chlorine
forms a
covalent
bond
with
itself
Cl2

20. How
will
two
chlorine
atoms
react? Cl Cl

21. Cl Cl Each chlorine atom wants to
gain one electron to achieve an octet

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

23. Cl Cl

24. Cl Cl

25. Cl Cl

26. Cl Cl

27. Cl Cl
octet

28. Cl Cl octet circle the electrons for each atom that completes
their octets

29. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle
circle the electrons for
each atom that completes
their octets

30. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle
Copy
circle the electrons for
each atom that completes
their octets

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

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

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

34. Single bonds are abbreviatedCl Cl
Single bonds are abbreviated
with a dash
circle the electrons for
each atom that completes
their octets

35. This is the chlorine molecule,Cl Cl
This is the chlorine molecule,
Cl2
Copy
circle the electrons for
each atom that completes
their octets

36. Cl-Cl
Structural formula Dot Structure

37. Two hydrogen atoms, each with 1 electron,
Covalent Bonding in H2
Two hydrogen atoms, each with 1 electron, H .
Practice
can share those electrons in a covalent bond. H :
Sharing the electron pair gives each hydrogen an electron configuration analogous to helium. 2

38. Two fluorine atoms, each with 7 valence electrons,
Covalent Bonding in F2
Two fluorine atoms, each with 7 valence electrons, .. .. F . :
Practice
can share those electrons in a covalent bond. F : ..
Sharing the electron pair gives each fluorine an electron configuration analogous to neon. 2

39. The Octet Rule
In forming compounds, atoms gain, lose, or share electrons to give a stable electron configuration characterized by 8 valence electrons. F : ..
The octet rule is the most useful in cases involving covalent bonds to C, N, O, and F. 2

40. to write a Lewis structure for CF4.
Example
Combine carbon (4 valence electrons) and four fluorines (7 valence electrons each) C . F : .. .
Practice
to write a Lewis structure for CF4. : F .. C
The octet rule is satisfied for carbon and each fluorine. 4

41. Example
It is common practice to represent a covalent bond by a line. We can rewrite : F .. C .. C F .. : as 4

42. Multiple Covalent Bonds
Sometimes atoms attain noble gas configuration by sharing 2 or 3 pairs of electrons
Double covalent bond and Triple covalent bond

43. Double Covalent Bonds
A Double Covalent Bond is a bond that involves 2 shared pairs of electrons (4 e-) between two atoms
Copy

44. O2
Oxygen is also one of the diatomic molecules

45. O
How will two oxygen atoms bond?

46. O
Each atom has two unpaired electrons

47. O

48. O

49. O

50. O

51. O

52. O

53. O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.

54. O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.

55. O

56. O O

57. O O

58. O O

59. Both electron pairs are shared.

60. O O
6 valence electrons
plus 2 shared electrons
= full octet

61. O O
6 valence electrons
plus 2 shared electrons
= full octet

62. O O
two bonding pairs,
making a double bond
Copy

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

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

65. O = oxygen O2 Chemical Name Chemical formula Dot structure
Structural formula
oxygen O2 O =

66. Triple Covalent Bond
A Triple Covalent Bond is a bond that involves 3 shared pairs of electrons (6 e-) between two atoms
Copy

67. Summary
In your notebooks explain why covalent bonds are formed. State the difference between a single, double and triple bond.
DO SUMARRY

68. General Rules
The central atom would usually be the less electronegative atom.
Hydrogen and group 17 elements are never central atoms.
Make sure all atoms have a full outer shell ( for Hydrogen 2 valence electrons, for all other elements 8 valence electrons)

69. Create a Table
Molecular Formula
Dot Structure of Atoms Present
Dot Structure of Molecule
Structural Formula
Types of covalent bonds present

70. Practice Lewis Dot Structure
Group 1: H2 N2 O2
Cl2
Br2 I2
Group 2: F2
HCl
CH4
H2O
NH3
H2Se
Group 3: HF
CO2
NI3
CBr4
HCN
H2S