1. Chemical Formulas and Names
Chapter 9 notes

2. Two types of compounds 1. Ionic compounds (ions)
Metal + nonmetal
2. Molecular compounds (covalent)
Nonmetal + nonmetal

3. Binary Ionic compounds
Binary compounds have two elements
Ionic has metal + nonmetal
To name a binary comp. – always name the cation first; then the anion.
Ex.
NaCl sodium chloride
CaCl2 calcium chloride
K2O potassium oxide

4. Transition Metals
Many have more than one charge possible. (not all Zn+2; Ag+1)
Use Roman numerals in name to tell the charge
Ex. Fe+2 is iron(II)
Fe+3 is iron (III)
Cu+2 is copper(II)

5. Polyatomic Ions
Groups of atoms with a charge. Names tend to end in –ite or –ate.
Treat same as a monoatomic ion.
Use ions list for the name and formula
Many negative ions are polyatomic.
Only one positive polyatomic ion.
NH4+1 ammonium ion

6. Writing formulas Formulas represent a neutral molecule
The charge of each ion must be considered.
When writing a formula for an ionic compound, the order is cation;anion and subscripts are used to tell the number of each ion present.

7. examples
Sodium chloride made of Na+1 and Cl-1 ions. Using one of each ion would make a neutral molecule.
Formula is NaCl (notice that charges are not written in the formula – but must be considered)
Calcium bromide Ca+2 and Br-1 ions
For each Ca+2 you need 2 Br-1 to make it neutral.
Formula is CaBr2

8. When a polyatomic ion is used and more than one is needed to balance the charges, parenthesis are used.
For example: copper(II) nitrate
Copper(II) ion charge
nitrate ion charge (2 ions needed)
Formula is Cu(NO3)2
Notice that charges are not written, and that the nitrate ion uses parenthesis.

9. Molecular compounds Two (or more) elements sharing e-.
molecules
Binary – two elements only
(nonmetal – nonmetal)
Compound names will end in –ide.
Numerical prefixes tell how many atoms of each element are present.

10. Numerical prefixes mono =1 hexa = 6 di =2 hepta = 7 tri = 3 octa = 8
tetra = 4 nona = 9
penta = 5 deca =10

11. examples CO2 carbon dioxide N2O dinitrogen monoxide
The name tells the number and types of atoms (in order)

12. Mono- Used for second element only
CO2 carbon dioxide (mono is not used)
CO carbon monoxide

13. Writing the formula from the name
Write the symbol for each element.
If there is a prefix, write the number as a subscript (below the line) after the symbol.
Example: nitrogen trichloride
(one nitrogen and three chlorine atoms)
NCl3

14. Try these Carbon tetrabromide Diphosphorus pentasulfide SO3 OF2
Practice!!!