1. “Ionic, Covalent and Metallic Bonding”
modified from
Stephen L. Cotton

2. Valence Electrons are…?
electrons in the outer energy level.
Responsible for properties of elements
Valence electrons - The s and p electrons in the highest occupied energy level
Core electrons – are those in the energy levels below.

3. Keeping Track of Electrons
Atoms in the same column...
Have the same outer electron configuration.
Have the same valence electrons.
The number of valence electrons are easily determined. It is the group number for a representative element
Group 2A: Be, Mg, Ca, etc.
have 2 valence electrons

4. Electron Dot diagrams are…
A way of showing & keeping track of valence electrons.
How to write them?
Write the symbol - it represents the nucleus and inner (core) electrons
Put one dot for each valence electron (8 maximum)
They don’t pair up until they have to (Hund’s rule) X

5. The Electron Dot diagram for Nitrogen
Nitrogen has 5 valence electrons to show.
First we write the symbol. N
Then add 1 electron at a time to each side.
Now they are forced to pair up.
We have now written the electron dot diagram for Nitrogen.

6. The Octet Rule
The Octet Rule: in forming compounds, atoms tend to achieve a noble gas configuration; 8 in the outer level is stable
Each noble gas (except He, which has 2) has 8 electrons in the outer level

7. Formation of Cations
Metals lose electrons to attain a noble gas configuration.
They make positive ions (cations)
If we look at the electron configuration, it makes sense to lose electrons:
Na 1s22s22p63s1 1 valence electron
Na1+ 1s22s22p6 This is a noble gas configuration with 8 electrons in the outer level.

8. Electron Dots For Cations
Metals will have few valence electrons (usually 3 or less); calcium has only 2 valence electrons Ca

9. Electron Dots For Cations
Metals will have few valence electrons
Metals will lose the valence electrons Ca

10. Electron Dots For Cations
Metals will have few valence electrons
Metals will lose the valence electrons
Forming positive ions
Ca2+
This is named the “calcium ion”.
NO DOTS are now shown for the cation.

11. Electron Configurations: Anions
Nonmetals gain electrons to attain noble gas configuration.
They make negative ions (anions)
S = 1s22s22p63s23p4 = 6 valence electrons
S2- = 1s22s22p63s23p6 = noble gas configuration.
Halide ions are ions from chlorine or other halogens that gain electrons

12. Electron Dots For Anions
Nonmetals will have many valence electrons (usually 5 or more)
They will gain electrons to fill outer shell. 3- P
(This is called the “phosphide ion”, and should show dots)

13. Bonds are…
Forces that hold groups of atoms together and make them function as a unit. Two types:
Ionic bonds – transfer of electrons (gained or lost; makes formula unit)
Covalent bonds – sharing of electrons. The resulting particle is called a “molecule”

14. Ionic Bonding
Anions and cations are held together by opposite charges (+ and -)
Ionic compounds are called salts.
Simplest ratio of elements in an ionic compound is called the formula unit.
The bond is formed through the transfer of electrons (lose and gain)
Electrons are transferred to achieve noble gas configuration.

15. Ionic Compounds
Also called SALTS
Made from: a CATION with an ANION (or literally from a metal combining with a nonmetal)

16. Ionic Bonding Na Cl
The metal (sodium) tends to lose its one electron from the outer level.
The nonmetal (chlorine) needs to gain one more to fill its outer level, and will accept the one electron that sodium is going to lose.

17. Ionic Bonding
Na+
Cl -
Note: Remember that NO DOTS are now shown for the cation!

19. Ionic Bonding
Lets do an example by combining calcium and phosphorus: Ca P
All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable).

20. Ionic Bonding Ca P

21. Ionic Bonding
Ca2+ P

22. Ionic Bonding
Ca2+ P Ca

23. Ionic Bonding
Ca2+
P 3- Ca

24. Ionic Bonding
Ca2+
P 3- Ca P

25. Ionic Bonding
Ca2+
P 3-
Ca2+ P

26. Ionic Bonding Ca
Ca2+
P 3-
Ca2+ P

27. Ionic Bonding Ca
Ca2+
P 3-
Ca2+ P

28. Ionic Bonding
Ca2+
Ca2+
P 3-
Ca2+
P 3-

29. = Ca3P2 Ionic Bonding Formula Unit
This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance.
For an ionic compound, the smallest representative particle is called a: Formula Unit

30. Properties of Ionic Compounds
Crystalline solids - a regular repeating arrangement of ions in the solid: Fig. 7.9, page 197
Ions are strongly bonded together.
Structure is rigid.
High melting points
Coordination number- number of ions of opposite charge surrounding it

31. NaCl CsCl TiO2 - Page 198 Coordination Numbers:
Both the sodium and chlorine have 6
NaCl
Both the cesium and chlorine have 8
CsCl
Each titanium has 6, and each oxygen has 3
TiO2

32. Do they Conduct?
Conducting electricity means allowing charges to move.
In a solid, the ions are locked in place.
Ionic solids are insulators.
When melted, the ions can move around.
Melted ionic compounds conduct.
NaCl: must get to about 800 ºC.
Dissolved in water, they also conduct (free to move in aqueous solutions)

33. - Page 198
The ions are free to move when they are molten (or in aqueous solution), and thus they are able to conduct the electric current.

34. Covalent Bonds
The word covalent is a combination of the prefix co- (from Latin com, meaning “with” or “together”), and the verb valere, meaning “to be strong”.
Two electrons shared together have the strength to hold two atoms together in a bond.

35. Molecules Many elements found in nature are in the form of molecules:
a neutral group of atoms joined together by covalent bonds.
For example, air contains oxygen molecules, consisting of two oxygen atoms joined covalently
Called a “diatomic molecule” (O2)

36. (diatomic hydrogen molecule)
The nuclei repel each other, since they both have a positive charge (like charges repel).
How does H2 form?
(diatomic hydrogen molecule) + + + +

37. How does H2 form? But, the nuclei are attracted to the electrons
They share the electrons, and this is called a “covalent bond”, and involves only NONMETALS! + +

38. Covalent bonds Nonmetals hold on to their valence electrons.
They can’t give away electrons to bond.
But still want noble gas configuration.
Get it by sharing valence electrons with each other = covalent bonding
By sharing, both atoms get to count the electrons toward a noble gas configuration.

39. Covalent bonding
Fluorine has seven valence electrons (but would like to have 8) F

40. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven F F

41. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

42. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

43. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

44. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

45. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons… F F

46. F F Covalent bonding …both end with full orbitals
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals F F

47. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals F F
8 Valence electrons

48. F F Covalent bonding Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals F F
8 Valence electrons

50. Molecular Compounds The formula for water is written as H2O
The subscript “2” behind hydrogen means there are 2 atoms of hydrogen; if there is only one atom, the subscript 1 is omitted
Molecular formulas do not tell any information about the structure (the arrangement of the various atoms).

51. - Page 215
These are some of the different ways to represent ammonia:
3. The ball and stick model is the BEST, because it shows a 3-dimensional arrangement.
1. The molecular formula shows how many atoms of each element are present
2. The structural formula ALSO shows the arrangement of these atoms!

52. A Single Covalent Bond is...
A sharing of two valence electrons.
Only nonmetals and hydrogen.
Different from an ionic bond because they actually form molecules.
Two specific atoms are joined.
In an ionic solid, you can’t tell which atom the electrons moved from or to

53. H O Water Each hydrogen has 1 valence electron
- Each hydrogen wants 1 more
The oxygen has 6 valence electrons
- The oxygen wants 2 more
They share to make each other complete H O

54. H O Water Put the pieces together The first hydrogen is happy
The oxygen still needs one more H O

55. H O H Water So, a second hydrogen attaches
Every atom has full energy levels
Note the two “unshared” pairs of electrons H O H

56. Multiple Bonds
Sometimes atoms share more than one pair of valence electrons.
A double bond is when atoms share two pairs of electrons (4 total)
A triple bond is when atoms share three pairs of electrons (6 total)
Table 8.1, p Know these 7 elements as diatomic:
Br2 I2 N2 Cl2 H2 O2 F2
What’s the deal with the oxygen dot diagram?

57. Dot diagram for Carbon dioxide
CO2 - Carbon is central atom ( more metallic )
Carbon has 4 valence electrons
Wants 4 more
Oxygen has 6 valence electrons
Wants 2 more C O

58. Carbon dioxide
Attaching 1 oxygen leaves the oxygen 1 short, and the carbon 3 short C O

59. Carbon dioxide
Attaching the second oxygen leaves both of the oxygen 1 short, and the carbon 2 short O C O

60. Carbon dioxide
The only solution is to share more O C O

61. Carbon dioxide
The only solution is to share more O C O

62. Carbon dioxide
The only solution is to share more O C O

63. Carbon dioxide
The only solution is to share more O C O

64. Carbon dioxide
The only solution is to share more O C O

65. Carbon dioxide
The only solution is to share more O C O

66. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond O C O

67. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond
8 valence electrons O C O

68. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond
8 valence electrons O C O

69. O C O Carbon dioxide The only solution is to share more
Requires two double bonds
Each atom can count all the electrons in the bond
8 valence electrons O C O

70. H C N HCN Put single bond between each atom Need to add 2 more bonds
Must go between C and N (Hydrogen is full) H C N

71. H C N HCN Put in single bonds Needs 2 more bonds
Must go between C and N, not the H
Uses 8 electrons – need 2 more to equal the 10 it has H C N

72. H C N HCN Put in single bonds Need 2 more bonds
Must go between C and N
Uses 8 electrons - 2 more to add
Must go on the N to fill its octet H C N

73. A Coordinate Covalent Bond...
When one atom donates both electrons in a covalent bond.
Carbon monoxide (CO) is a good example:
Both the carbon and oxygen give another single electron to share O C

74. Coordinate Covalent Bond
When one atom donates both electrons in a covalent bond.
Carbon monoxide (CO) is a good example:
Oxygen gives both of these electrons, since it has no more singles to share.
This carbon electron moves to make a pair with the other single. C O

75. Coordinate Covalent Bond
When one atom donates both electrons in a covalent bond.
Carbon monoxide (CO)
The coordinate covalent bond is shown with an arrow as: C O
C O

76. Metallic Bonds are… How metal atoms are held together in the solid.
Metals hold on to their valence electrons very weakly.
Think of them as positive ions (cations) floating in a sea of electrons: Fig. 7.12, p.201

77. Sea of Electrons + Electrons are free to move through the solid.
Metals conduct electricity. +

78. Metals are Malleable
Hammered into shape (bend).
Also ductile - drawn into wires.
Both malleability and ductility explained in terms of the mobility of the valence electrons

79. Due to the mobility of the valence electrons, metals have:
- Page 201
Due to the mobility of the valence electrons, metals have:
Notice that the ionic crystal breaks due to ion repulsion!
1) Ductility
2) Malleability
and

80. Malleable +
Force

81. Malleable + + + + Force + + + + + + + +
Mobile electrons allow atoms to slide by, sort of like ball bearings in oil. + + + +
Force + + + + + + + +

82. Ionic solids are brittle
Force + -

83. Ionic solids are brittle
Strong Repulsion breaks a crystal apart, due to similar ions being next to each other. + -
Force + - + - + -