1. IPC 03B Chemical Bonding

2. Number of Valence Electrons
Valence Electrons: Are electrons in the highest energy level. The noble gases have 8 electrons.
Group 1 has 1 v.e-
Group 2 has 2 v.e-
Group 17 has 7 v.e-
Group 18 has 8 v.e-
Group 13 has 3 v.e-

3. Valence electrons are represented using dot diagrams.
Valence electrons (dots) are placed around the four sides of the element symbol.
Electrons (dots) begin to pair up only when no more single spaces are left.

4. Octet Rule: atoms will gain, lose, or share e- in order to have 8 valence e- and become stable.
Exception: the first energy level only needs 2 valence electrons to be stable.
So, Helium is stable and will not bond with other atoms.

5. Stable Atoms
Atoms with less than 8 valence electrons are not very stable.
Atoms with 8 valence electrons are very stable.
Helium is stable with two electrons.
Chlorine has 7 valence electrons (not stable).
Chlorine gains an electron to have 8 valence electrons (stable).

6. Are these elements stable?
A sodium atom is unstable because it has only one valence e-.
A neon atom is stable because it has an octet (8 valence e-).

7. Stable atoms have full valence shells.
Lithium atoms have 3 e-. Since the 1st energy level only holds 2 e-, lithium has 1 valence e-.
If lithium loses that electron, it will have a full valence shell with 2 e- and an oxidation number of +1.
Li + Li

8. Metals will lose electrons to form positive ions.
Net Ionic Charges
Metals will lose electrons to form positive ions.
Nonmetals will gain electrons to form negative ions.

9. Groups/Families Group Number Group Name Valence Electrons
Oxidation Number 1
Alkali Metals +1 2
Alkaline Metals +2
3-12
Transition Metals
Vary 13
Boron Family 3 +3 14
Carbon Family 4
+/4 15
Nitrogen Family 5 3 16
Oxygen Family 6 2 17
Halogens 7 1 18
Noble Gases 8

10. Chemical Bonds Compounds are made up of more than one atom.
When atoms combine to make molecules, they form chemical bonds.
Types of Bonds:
Ionic Bonds
Covalent Bonds
Metallic Bonds

11. Ionic Bonding

12. Ions: atoms with a positive (+) or negative (-) charge.
Metals tend to lose electrons to form positive ions called cations.
Sodium ion
Nonmetals tend to gain electrons to form negative ions called anions.
Chloride ion

13. opposite charges attract
Bond Formation:
electrons are transferred from a metal atom to a nonmetal atom
+11
-11
+17
-17
+17
-18
+11
-10
opposite charges attract

14. Write the charges on your periodic table!
Oxidation Numbers
No Ions!
Write the charges on your periodic table! -1

15. 6 Steps to Writing Ionic Compounds
Identify the (+) ion and the () ion.
Write the symbols with their charges.
Cross  the charges.
Remove the charges.
Simplify the numbers.
Remove the “1”s and write the formula.
Magnesium Sulfide
Mg+2 S-2
Mg-2 S+2
Mg2 S2
Mg1 S1
MgS
______________
(+) ion
_________
() ion
see periodic table
Both #’s are divisible by 2.
Metal first; then nonmetal.
Tutorial

16. Practice Steps Na-1 Na+1 Cl+1 Cl-1 Na1Cl1 NaCl Al+3 Al-2 S+3 S-2
Identify the (+) ion and the () ion.
Write the symbols with their charges.
Cross  the charges.
Remove the charges.
Simplify the numbers.
Remove the “1”s and write the formula.
Sodium Chloride
Aluminum Sulfide
__________
(+) ion
__________
() ion
Na-1
Na+1
Cl+1
Cl-1
Na1Cl1
NaCl
_____________
(+) ion
__________
() ion
Al+3
Al-2
S+3
S-2
Al2S3
Al2S3

17. Al+3 S-2 Al2S3 -2 +3 +6 + -6 = 0 Reason: Total Charges = Zero
Aluminum Sulfide
Al+3 S-2
Al2S3 -2 +3
Need 2 Al+3 ions
Need 3 S-2 Ions
S2-
Al3+
Al3+
S2-
S2-
= 0

18. Polyatomic Ions (EOC)

19. Ca(OH)2 -1 Ca2+ -1 Combining Atoms
Positive ions must cancel the negative ions to make a neutral molecule. -1
If you need more than one polyatomic ion, use ( ).
Ca2+ -1
Ca(OH)2

20. Al+3 (SO4)-2 Al2(SO4)3 -2 +3 +6 + -6 = 0 Aluminum Sulfate
Put ( )’s around the polyatomic ions so you don’t get the numbers confused.
Al+3 (SO4)-2
Al2(SO4)3 -2 +3
Need 2 Al+3 ions
Need 3 SO4-2 Ions
Al3+
Al3+
= 0

21. Properties of Ionic Compounds (Salts)
Made up of metal
w/ nonmetal
solid, crystalline structure
high melting point

22. Some soluble in water
hard or brittle
(not malleable)
conduct electricity
when melted or dissolved
nonconductor
as a solid

23. Covalent Bonding in Action

24. Covalent Bonding
Covalent Bond: Shared pair of electrons between two nonmetals.
Covalent compounds are called molecular compounds.

25. Atoms share electrons in order to get 8 valence electrons
Atoms share electrons in order to get 8 valence electrons. (Remember the Octet Rule) (Exception: only 2 e- for H)

26. H2 (g) O2 (g) F2 (g) Br2 (l) I2 (s) N2 (g) Cl2 (g)
Diatomic Elements 7- Up
H2 (g) O2 (g) F2 (g) Br2 (l) I2 (s) N2 (g) Cl2 (g)
“HOFBrINCl”
Diatomic means “2 atoms”
These 7 elements exist in nature as diatomic molecules (covalently bond).

27. Greek Prefixes
Prefix
Meaning
Mono- 1
Di- 2
Tri- 3
Tetra- 4
Penta- 5
Hexa- 6
Hepta- 7
Octa- 8
Nona- 9
Deca- 10
Don’t use prefix “mono” on the first element, only on the second.
Certain vowel combinations are not allowed: oo and ao
Ex. Don’t write tetraoxide; do write tetroxide.

28. Naming Molecular Compounds
First Nonmetal: (Greek prefix + element name)
Second Nonmetal: (Greek prefix + element root + -ide ending)

29. CCl4 SO3 N2O P2O5 CO2 SF6 Practice: Carbon Tetrachloride
Sulfur Trioxide
Dinitrogen monoxide
Diphosphorous pentoxide
Carbon Dioxide
Sulfur Hexafluoride

30. Writing Molecular Compounds
nonmetal with nonmetal: Write the element symbol followed by the Greek prefix as a subscript for both elements.

31. Phosphorus pentachloride
Practice:
Dinitrogen tetroxide
Carbon monoxide
Sulfur dioxide
Phosphorus pentachloride
N2O4 CO
SO2
PCl5

32. Type of Chemical Bond Ionic Bonds have ions!
Metal & Nonmetal
Polyatomic ion & Nonmetal
Polyatomic ion & Polyatomic ion
Attraction between pos. & neg. ions
Covalent Bonds have nonmetals!
Nonmetal & Nonmetal
Sharing of electrons

33. Metallic Bonds (free e-)

34. Metallic Bond
The metal is held together by the strong forces of attraction between the positive nuclei of the metallic cation and the “free floating” valence electrons known as a “Sea of Electrons”.
Sea of Electrons