1. Chapter 22: Chemical Bonding

2. Section 1– Electrons and Chemical Bonding
Chemical bonding – joining of atoms to form new substances
Chemical bond – interaction that holds 2 atoms together

3. Valence Electrons e- in outermost shell
Determines an atom’s chemical properties
Used to form bonds
Within a group, or family, atoms have the same # of valence e-
Atoms with fewer than 8 valence e- are more likely to form bonds than an atom with 8 e-

5. Types of Bonds Ionic, Covalent, Metallic
Atoms bond by sharing, gaining or losing e- to have a filled outermost energy level.
A full set = 2 e- for a few of the elements
A full set = 8 e- for most elements
Which ones? Why?

6. Section 2: Ionic Bonds
Bonds form by gaining or losing e-, resulting in charged atoms called ions.
Oppositely charged ions are attracted to one another
Metal + Nonmetal
Positive and negative charges cancel each other out to form an overall neutral compound

7. Metal Atoms Have few valence electrons
Usually lose these valence e- and form positive ions (cations)
Some transition metal ions can have multiple charges. For example, iron can have a +2 or a +3 charge.
The charge is written as a superscript of the symbol:
Ex. K+, Ca2+, Al3+

8. Nonmetal atoms Have almost full valence shells
Tend to gain e- from other atoms and form negative ions (anions)
The charge is written as a superscript of the formula:
Ex. P3-, S2-, Cl-

9. Polyatomic Ions Poly = “many” Polyatomic = “many atoms”
A group of atoms that behave as a single ion with an overall positive or negative charge
Treat the polyatomic ion as a single unit with a single charge.

11. Writing formulas for ionic compounds
The number of positive charges and negative charges must balance in an ionic compound
The formula represents this balance
Subscripts are used to indicate the ratio of elements in the compound (no “1”)

12. Writing formulas for ionic compounds
Find oxidation number (charge) for both parts
For elements in groups 1 and 2, use group #. Boron family is 3+, Carbon family ± 4, Nitrogen family is -3, Oxygen family is -2 and halogens are -1.
For cations followed by a roman numeral, the roman numeral is the oxidation #
For polyatomic ions check the list. Do not change the subscripts within the polyatomic ion formula.
----- Meeting Notes (2/7/13 10:56) -----
go to periodic table

13. 2. Write symbols. The positive ion first and negative ion second.
3. Put polyatomic ions in parentheses if more than one is needed.
4. Use subscripts to designate the number of each part for the total + and – charges to be =
a. Find the least common multiple of both charges
b. determine the factor needed to get that charge and use that as the subscript.

14. Sodium sulfide
Potassium iodide
Lithium oxide
Barium fluoride
Iron(III) oxide
Copper(II) chloride
g. Sodium acetate
h. Zinc(II) carbonate
i. Chromium(II) sulfate
j. Cobalt(III) iodide

15. Answers Na2S KI Li2O BaF2 Fe2O3
f. CuCl2 g. NaC2H3O2 h. ZnCO3 i. CrSO4 j. CoI3

16. Writing names for ionic compounds
Write the names of the + and - part of the formula
The + part is the name of the element or polyatomic ion
Check the list of elements to see if it needs a roman numeral. If so, use the negative part of the formula to figure out the positive charge on the metal.
To name the second/- part, if it is an element change the ending to “-ide”
If it is a polyatomic ion, keep the name as is

17. Practice LiCl MgCl2 g. (NH4)3PO4 h. ZnCO3 BeO i. Sn(OH)2 CaCl2
HgS
SnF2
g. (NH4)3PO4
h. ZnCO3
i. Sn(OH)2
j. Li2SO4
k. KC2H3O2

18. Answers Lithium chloride Magnesium Chloride Beryllium oxide
Calcium Chloride
Mercury(II) sulfide
Tin(II) fluoride
g. Ammonium phosphate
h. Zinc(II) carbonate
i. Tin(II) hydroxide
j. Lithium sulfate
k. Potassium acetate

19. 

20. Section 3: Covalent and Metallic Bonds
Covalent bonds are formed when atoms share one or more pairs of valence e-.
Forms between 2 nonmetals.
Covalent bonds result in the formation of molecules.
Define molecule

21. Octet Rule
Atoms combine in such a way so as to fill the valence shell (usually that means 8 e- but could be just 2 e-)

22. How many bonds?
The number of e- that an atom needs to fulfill it’s valence is equal to the number of covalent bonds it can form.
Ex. N can make 3 covalent bonds because it has 5 e- in its valence shell
Ex. H can make 1 covalent bond because it has 1 e- its valence shell.

23. Diatomic Elements
Certain elements exist as pairs in nature because that is how they are most stable.
Di = 2
Just remember Professor BrINClHOF (Bromine, Iodine, Nitrogen, Chlorine, Hydrogen, Oxygen and Fluorine)
You need to memorize the 7 diatomic elements!!

24. Practice! Draw a Bohr diagram and Lewis structure for the following:
Water (H2O)
Diatomic Fluorine (F2)
Silicon tetrafluoride (SiF4)

25. Double Bonds
When atoms share 2 pairs of e-, it is a double bond

26. Triple Bonds
When atoms share 3 pairs of e-, it is a triple bond

27. Naming Covalent Compounds
Many compounds have common names such as "methane", "ammonia" and "water”
Simple covalent compounds can be named using prefixes to indicate how many atoms of each element are in the formula.
The ending of the last (most negative) element is changed to -ide.

28. Naming Covalent Compounds
Prefixes:
Mono = 1
Di = 2
Tri = 3
Tetra = 4
Penta = 5
Hexa = 6
*If there is just 1 of the first element no prefix is used

29. Practice
CO2
SiF4 CO
NBr3
P2O5
BCl3

30. Answers CO2 – carbon dioxide SiF4 – silicon tetrafluoride
CO – carbon monoxide
NBr3 – nitrogen tribromide
P2O5 – diphosphorus pentoxide
BCl3 - boron trichloride

31. Practice Carbon tetrabromide Phosphorus triiodide Bromine
silicon monoxide
Silicon disulfide

32. Answers
CBr4
PI3
Br2 (Bromine is a diatomic molecule!)
SiO
SiS2

33. Metallic Bonds
A bond formed by the attraction between positively charged metal ions and surrounding e-
Think of a metal as being made up of positive ions with electrons “swimming” around keeping the ions together

34. Properties of Metals
Because e- can move freely about, metals have particular propeties.

35. Conduct electricity well

36. Metals can be reshaped (ductile, malleable)

37. Metals can bend without breaking