1. M A R C H 2 3 , 2 0 1 5
Naming and Writing
Compounds and Molecules

2. Objectives
1. Write formulas for and name ionic compounds
2. Write the formulas for and name covalent
molecules

3. Writing Ionic Formulas
Example: calcium bromide
1. Write the symbols of both ions
Ca Br
2. Using the crossover method determine the number
of each ion.
Ca+2Br-1
Therefore:
CaBr2

4. Polyatomic ions
Example: Magnesium Nitrate
1. Look up the formula and charge for nitrate on
polyatomic ion list.
2. Write the symbols of ion and polyatomic ion
Mg NO3
3. Using crossover method determine number of each
ion. Use parenthesis in the formula for polyatomic ions
with a subscript
Mg+2[NO3]-1
Therefore:
Mg(NO3)2

5. Practice
Sodium Fluoride
NaF
Aluminum Sulfate
Al2(SO4)3

6. Naming Ionic Compounds
Example: NaI
 Write the name of the first ion, add the suffix “ide” to the
second ion.
Sodium Iodide
Polyatomic ion example: NaOH
 Look up the formula and charge of polyatomic ion. Write
name of first ion and name of polyatomic ion
Sodium Hydroxide

7. Practice
BaSO4
Barium Sulfate
AgCl
silver chloride

8. Writing Covalent Formulas
Example: Dinitrogen tetraflouride
1. Write the symbol of the first and second element
N F
2. Numbers are given in greek prefixes, write the
subscript that the prefix indicates
N2F4

9. Practice
carbon trioxide
CO3
dihydrogen monoxide
H2O

10. Naming Covalent Molecules
Example: N2S4
1. Write the name of the first element and add the suffix
“ide” to the second
Nitrogen Sulfide
2. Use greek prefixes to indicate the number of
atoms in the formula
*do not use mono in the first element
* drop o or a in greek prefix if element starts with a vowel
Dinitrogen tetrasulfide

11. Practice
N2O5
dinitrogen pentoxide
Br2I4
dibromine tetriodide