1. Writing Ionic Formulas
Chapter 8 Notes
Writing Ionic Formulas

2. Compounds Up until now, we have only looked at single elements.
There are just over 100 elements, so how do we account for there being so many different types of stuff?

3. Compounds
There are millions of different compounds —two or more elements that are combined chemically.
The two types of compounds we will discuss in this chapter are ionic compounds and covalent compounds.

4. A compound is a pure substance made up of two or more elements that are chemically joined in definite proportions. Ex. Carbon dioxide is CO2 , while carbon monoxide (the poison) is CO .
2 oxygen atoms
1 oxygen atom

5. Compounds do not look or act like the elements that form them.

6. Chlorine is a poisonous, green gas.
Sodium is a silvery metal that reacts violently with water
Chlorine is a poisonous, green gas.
Does salt share any of those properties?

7. Oxygen + Hydrogen -----> Water
Hydrogen is explosive!
Is water explosive?

8. Ionic Compounds
Last chapter we discussed ions—elements that have a charge due to losing or gaining electrons.
Ionic compounds are made of ions.

9. Ionic Compounds
Metals lose electrons, giving them an overall (+) charge. These are called cations.
Nonmetals gain electrons, giving them an overall (-)charge. These are called anions.

10. Ionic Compounds
An ionic compounds is formed by combining a cation (metal) and an anion (nonmetal).

11. Oxidation number: the charge of an atom, indicating whether the atom has lost (+) or gained (-) electrons and how many electrons it lost or gained.
Superscript +3 Al

12. Oxidation Numbers Group Lose or gain electrons How many Oxidation1 +1 2A 2 +2 3A 3 +3 4A 4
+4 or -4 5A
gain -3 6A -2 7A -1 8A
none

13. Ionic compounds consist of two oppositely charged ions. Li+1 F-1
Positive ion – metal
Negative ion - nonmetal
F-1 F0
9p+
10n0
Li+1
Li0
3p+
4n0

14. Mg+2
Na+1
Al+3
Cl-1
O-2
P-3
Single or Monoatomic ions

15. Polyatomic Ions
Anions and cations can also be made up of a group of elements bonded together that carry an overall charge.
These groups of elements are called polyatomic ions.

16. Polyatomic ions - groups of 2 or more elements that have a charge
NH4+1
SO3-2
PO4-3
ClO3-1
SO4-2
NO3-1
C2H3O2-1
NO4-1
CO3-2

17. Chemical Formulas
A chemical formula tells you the type and number of each element in the compound.
(like the recipe of a compound)
Na2SO4
Ba3(PO4)2

18. Formulas consist of a positive ion and a negative ion.
Mg+2
Na+1
The positive ion always comes 1st
Al+3
Cl-1
O-2
P-3
AlP
NaCl
MgO

19. Subscript - a small lowered number that shows number of atoms of each element in the compound.
Ba3P2 P P Ba Ba Ba

20. A subscript of (1)
is NEVER written.
NO!!!
Na1Cl1

21. Even though an ionic compound is made from charged particles, it’s total charge is always
EQUAL TO ZERO!!!
CaO Ca
Ca+2 O
O-2
+2 -2 = 0

22. Binary compounds: composed of only two elements
Binary compounds: composed of only two elements. (Look for 2 capital letters!) Ex. NaCl sodium chloride Ex. Mg3N2 magnesium nitride

23. Ternary compounds: NaC2H3O2 2 3 4 1
composed of three or more elements and contain at least one polyatomic ion (Look for 3 or more capital letters) 2 3 4 1
NaC2H3O2

24. Ex. Na ClO3 sodium chlorate Ex. Ca3 (PO4)2 calcium phosphate

25. Variable vs Non-variable Metals
Look at the chart on the back of
periodic table.
If the metal is on the back of the periodic table with more than one oxidation number
listed it is variable.
EX: Cr= +2, +3, or +6
Fe= +2, or +3

26. If it is not on the back of
NON VARIABLE
If it is not on the back of
the periodic table OR
Only one choice of oxidation number listed. EX: Ag+1, Zn+2, or Ni+2
Then it is non variable

27. Roman Numerals
Used when a metal has more than one potential oxidation number
The name of the metal must tell you the valence of the metal

28. Chromium chloride
III
The Roman numeral three tells you that the oxidation number of the metal is +3.
III

29. Chromium chloride VI
The Roman numeral six tells you that the oxidation number of the metal is +6. VI

30. Writing and Naming Ionic Compounds

31. Writing Chemical Formulas
1) Write the symbol for the elements and their oxidation number, positive ion first (the metal).
EX: For a compound of Magnesium and Chlorine Mg +2 -1 Cl

32. Writing Chemical Formulas
2) Criss cross the numbers and write them as subscripts without the signs. Mg +2 2 -1 1 Cl

33. Writing Chemical Formulas
3) If there is a one charge, do not write it.
Mg Cl2
Mg1Cl2

34. Writing Chemical Formulas
4) If you have subscripts that are multiples, reduce them down. +4 4 -2 2 Pb O 1 2

35. Naming Ionic Compounds
For ionic compounds where the metal always has the same oxidation number,
1) Name the metal.
EX: BaBr2
Barium

36. Naming Ionic Compounds
For ionic compounds where the metal always has the same oxidation number,
2) Write the name of the non-metal, and change the end to –ide.
EX: BaBr2
Barium
brom
ine
ide

37. Naming Binary Non variable Compounds
Name the positive ion
Name the negative ion
changing the ending to IDE.
AlBr3
Aluminum bromide
No Roman numeral is needed

38. -ides N - Nitrogen--> Nitride O – Oxygen --> Oxide
F - Fluorine--> Fluoride
P - Phosphorus--> Phosphide
S - Sulfur--> Sulfide
Cl - Chlorine-->Chloride
Br - Bromine -->Bromide
I - Iodine--> Iodide

39. Naming Polyatomic Non variable Compounds
Name the positive ion
Name the negative ion
changing the ending to -ate.
AlPO4
Aluminum
Phosphate
No Roman numeral is needed

40. Naming Ionic Compounds
If there is a polyatomic anion, then you do not change the ending:
EX: Ca(NO3)2
Calcium
nitrate

41. Name These:
Na2O
MgCl2
Na2CO3

42. Naming binary compounds of variable metals
Determine the oxidation number of the variable metal using the crisscross method
Cr2O3
Cr+ O-
The oxidation number of the chromium is +3
The name is Chromium III oxide 2 3

43. Naming Ionic Compounds
If a positive ion (a metal) can have more than one oxidation number, you have to designate its charge in the name!
We do this by putting the charge as a roman numeral in parenthesis between the positive and negative ion.

44. Naming Ionic Compounds
Why do we need to do that?
Name: Fe2O3
FeO
These both exist in nature, so we have to show which one we mean.

45. Naming Ionic Compounds+3
Reverse criss cross to find the charge of the iron:
If this is true, then what was iron to begin with?
Fe2O3
Name it: -2
Iron ( ) ox
ygen
ide
III

46. Naming Ionic Compounds+2 -2
Reverse criss cross to find the charge of the iron:
If this is not true, the numbers must have been reduced.
Fe O
Name it: -1
Iron ( ) ox
ide
ygen II

47. Naming Ionic Compounds
Metals that don’t need parentheses:
Group I, II and IIIA
Zn, Cd (always +2) and Ag (always +1)
Which means transition, inner transition and other metals do!

48. Naming polyatomic compounds of variable metals
Determine the valence of the variable metal using the crisscross method
Hg2SO4
Hg+ SO4-
The oxidation number of the Mercury is +1
Mercury I sulfate 2 1

49. Naming Ionic Compounds
Final flowchart of how to name:
Name the positive ion.
Does it need a roman numeral?
If so, reverse criss cross, if not, ignore.
Name the negative ion and:
If a nonmetal end in -ide; if not, end normally

50. Name these:
Na2S
CuCl2
K2SO4
Pb(NO3)3

51. Calcium nitrate Ca +2 NO3-1 2. Add the oxidation numbers together.
Finding formulas
Determine the charge of each
side of the formula.
Nonvariables:
Aluminum oxide: Al+3 O-2
Potassium Chloride K+1 Cl-1
Calcium nitrate Ca +2 NO3-1
2. Add the oxidation numbers together.
+3-2 = = = +1

52. 2. Add the oxidation numbers
together.
Al+3 O K+1 Cl-1
+3-2 = = 0
3. If the total = zero the formula is balanced with one
ion each ex: KCl

53. If the total does not equal zero
use the crisscross method to
determine the number of ions
needed for each side of the
formula. 3 2
Al+3 O-2
Al O

54. If the total does not equal zero
use the crisscross method to
determine the number of ions
needed for each side of the
formula. 3 2
Al+3 SO4 -2
Al SO4 ( )

55. Writing Chemical Formulas
5) If using polyatomic ions, put parentheses if there are more than one. +2 2 ( -1 1 ) Ca
NO3

56. Writing Chemical Formulas
Here’s an example of a polyatomic that doesn’t have parentheses. +1 1 -3 3 Na
PO4

57. BaCl2 Rb3N Li3PO4 Fe(NO3)3 MnS2 Practice These: Barium and chlorine
Rubidium and nitrogen
Lithium and phosphate
Iron (III) and nitrate
Manganese (IV) and sulfur
BaCl2
Rb3N
Li3PO4
Fe(NO3)3
MnS2

58. Chapter 8 Notes: Part III
Bonding in Metals

59. Metallic Bonds
Metallic bonds consist of metal cations with a free-floating “sea of electrons”
This explains many physical properties—why metals are good conductors, and why they are malleable and ductile

60. Malleablilty/Ductility
Ductile – the ablity to be drawn into wires
Malleable – the ablity to be hammered into shapes

61. Malleablilty/Ductility
Metals display these characteristics because when subjected to pressure, cations can easily slide past one another (unlike ionic solids, which have very strong attractive and repulsive forces)

62. Alloys
Most metals you use everyday are a mixture of two or more elements, for example brass, bronze or steel. These are called alloys.

63. Alloys
The importance of alloys are that often they have superior properties than the elements they are made of.

64. Oxyanions
An oxyanion is a polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms. Many oxyaions contain the same nonmetal and have the same charges but differ in the number of oxygen atoms.

65. These ions are easily named using the following conventions.
The ion with more oxygen atoms is named using the root of the nonmetal plus the suffix-ate.
The ion with fewer oxygen atoms is named using the root of the nonmetal plus the suffix-ite.

66. Halogens form four oxyanions
The ion with the greatest number of oxygen atoms is named using the prefix per-, the root of the nonmetal, and the suffix –ate.
The ion with one less oxygen atom is named with the root of the nonmetal and the suffix –ate.
The ion two fewer oxygen atoms is named using the root of the nonmetal plus the suffix –ite.

67. The ion with three fewer oxygen atoms is named using the prefix hypo-, the root of the nonmetal, and the suffix –ite.