1. Naming and Formulas Chapter 9-10
Unit 7
Naming and Formulas
Chapter 9-10

2. Ionic Compounds
Ionic compounds are electrically neutral, even though they are composed of charged ions
Total positive charge equals total negative charge

3. Determining Formulas Must be electrically neutral
Total positive charge must equal total negative charge
Use oxidation numbers from Periodic Table
Group 1  +1 Group 2  +2
Group 13  +3 Group 15  -3
Group 16  -2 Group 17  -1

4. Determining Formulas
Determine number of each ion to balance out charge
Use as subscript for element symbol
Ex: CaCl2, Na3PO4, Mg(NO3)2
Write Positive Ion First
Formula must be smallest whole-number ratio

5. Example
Sodium and Chlorine
Na+
Cl-
Na1Cl1
NaCl

6. Example
Calcium and Fluorine
Ca+2 F- F-
Ca1F2
CaF2

7. Examples
Potassium and Oxygen K+ K+
O-2
K2O1
K2O

8. Polyatomic Ions
Group of atoms that collectively have gained or lost electrons (Table E)
Sodium and Nitrate
Na+
(NO3)-
Na1(NO3)1
NaNO3

9. More Examples
Potassium and Sulfate
Ammonium and Sulfur
K2SO4
(NH4)2S

10. Short-cut (criss-cross method)
Magnesium and Phosphate
Mg+2
PO4-3
Mg3(PO4)2

11. Short-cut (criss-cross method)
Magnesium and Carbonate
Mg+2
CO3-2
Mg2(CO3)2
Must Simplify
MgCO3

13. Naming Ions Positive Ions, cations, simply retain their name.
Na+  Sodium Ion
Mg2+  Magnesium Ion

14. Naming Ions Negative Ions, anions, change ending of element to –ide
Cl-  Chloride Ion
Br-  Bromide Ion

15. Unique Anions Names N3-  Nitride Ion O2-  Oxide Ion
S2-  Sulfide Ion
P3-  Phosphide Ion

16. Polyatomic Ions
Selected polyatomic ions are on Table E in the Reference Tables.
Polyatomic ions keep their names in most chemical names

17. Naming Systems Ionic System Binary Covalent System (Prefixes)
Stock System (Roman Numerals)
Binary Covalent System (Prefixes)

18. When to use ionic system
First element is a metal
NaCl
More than 2 elements, meaning polyatomic ion is involved
NH4Cl

19. Naming Ionic Compounds
Name positive ion first, then negative ion.
NaCl  Sodium chloride
Fe(OH)2  Iron(II) hydroxide

21. Stock System
Used when the metal has more than one positive oxidation number
Use a roman numeral to indicate the charge of the ion

22. Roman Numerals Cation Charge Roman Numeral +1 I +2 II +3 III +4 IV +5+6 VI +7
VII +8
VIII

23. Stock System Examples Fe+2  Iron(II) Cu+  Copper(I)
Mn+7  Manganese(VII)
Au+3  Gold(III)
Cr+6  Chromium(VI)
Pb+4  Lead(IV)

25. Binary Covalent Compounds
Use when compound is 2 nonmetals
Including metalloids
Use a prefix system to indicate the number of atoms for each element
Second element ends in -ide

26. Prefixes Number of atoms Prefix 1 mono- 2 di- 3 tri- 4 tetra- 5 penta-6
hexa- 7
hepta- 8
octa-

27. Example
N2Cl3
Dinitrogen Trichloride

28. Exceptions
When there is only one atom of the first element, do not use mono- prefix.
CO2
Carbon dioxide
OF2
Oxygen difluoride

29. Exceptions
When an element starts with a vowel, drop any o or a at the end of a prefix CO
Carbon Monooxide
Carbon Monoxide
P2O5
Diphosphorus Pentaoxide
Diphosphorus Pentoxide