Chem Formula

Not good at naming ions? No worries! With these few simple tricks you will be a pro shortly!

Step 1: Determine whether the compound is ionic or covalent.

• An ionic compound will have one non-metal element and one metal element
• Ex:  NaCl (Sodium is a metal and Chloride is a non-metal)
• A covalent compound (often referred to as molecular) has two non-metal elements
• Ex: CO (Carbon and Oxygen are both non-metals)

Step 2:  Ionic compounds must have a net charge of 0.

• Using the periodic table, determine the charge of each ion.
• Ex: Alkali metals (Lithium, Potassium) have a +1 charge.  Alkaline earth metals (Magnesium, Calcium) have a +2 charge.
• For NaCl we know that Na has a +1 charge and Cl has a -1 charge.
• Determine whether or not a roman numeral must be used.
• Ex: Fe (Iron) has a +2 and +3 charge, which is important to note when used in a compound.
• Determine if multiples of an ion or element are required to balance out the net charge.
• Ex: (Li)3PO4 means that the Lithium ion must be multiplied by three to balance the Phosphates -3 charge.  In the case of Potassium permanganate, the charges balance out (a +1 and a -1) so no multiplication is needed.

Step 3:  Covalent compounds use a special prefix system for naming.

• Determine the charges of each ion 
• Ex: ClF (Chlorine has a -1 charge and Fluorine has a -1 charge)
• Based on the molecular formula, name the molecule based of the number of elements.
• Ex: Cl2O would be named Dichlorine monoxide, di- for two chlorines and mono- for one oxygen.  N2O5 would be named Dinitrogen pentoxide, di- for two nitrogens and penta- for five oxygens.

Numerical Prefixes

mono: 1

di: 2

tri: 3

tetra: 4

penta: 5

hexa: 6

hepta: 7

octa: 8

nona: 9

deca: 10