Naming and Formulas Help Sheet
Covalent Compounds:
Compounds consist of elements ONLY from the right side of the stair step. ALL NONMETALS!!! Remember: H is a nonmetal even though it is on the left side of the table.
Use numerical prefixes when naming the compound.
Ex: BCl3 à Boron trichloride Tri: means 3
When writing the formula write EXACTLY what the numerical prefixes tell you to write: NO CRISS CROSSING!!!
Ex: Carbon tetrachloride à CCl4 tetra means 4 chlorines!
Ionic Compounds:
Ionic compounds consist of elements that have at least one from the left side of the table: METALS!!!
To write an ionic formula you must criss cross the charges of the elements involved. The charges are taken from the pattern on the periodic table:
Follow the directions below to write an ionic compound formula:
The following is writing ionic compound formulas that involve polyatomic ions:
To name an ionic compound all you have to do is name what you see (no numerical prefixes) and change the ending to “ide” if taken from the periodic table. If the compound has a polyatomic ion in it you only name what you see with no changes;
Ex: K2SO4 à Potassium Sulfate à Sulfate is a polyatomic ion, you do not change the ending
MgCl2 à Magnesium Chloride à you must change the ending of Chlorine to “ide”
NUMERICAL PREFIXES ARE NOT USED FOR IONIC COMPOUNDS!!!
Ionic Compounds with Transition Metals:
The very center of the periodic table is the Transition Metals:
The transition metals MUST include a roman numeral to indicate their charge when you write the name. The roman numeral in the name is also the charge of the transition metal.
Ex: Iron (II) Chloride à Fe2+ Cl-1 2+ is the charge of iron we know this from the roman numeral.
If writing the name from the formula you must do this:
FeCl2 The 2 under the chlorine came from the iron when it was criss crossed, so you need to include the charge as a roman numeral in the name!
Ex: FeCl2 à Iron (II) Chloride