Ionic formula
How do you write the formula of an ionic compound?
The chemical formula of an ionic compound shows the ratio positive and negative ions in the compound.
For example magnesium chloride has the chemical formula of MgCl2.
The ratio of magnesium and chloride ions is one to two or Mg2+ : Cl- = 1 : 2
An ionic compound is made up of positive and negative ions.
The following table of ionic compounds shows the ratio of ions needed to produce a neutral compound.
| Ionic compound | Metallic ions | Non metallic ions | Ratio of ions | Chemica formula |
| Sodium chloride | Na+ | Cl- | 1:1 | NaCl |
| Sodium oxide |
Na+ Na+ |
O2- | 2:1 | Na2O |
| Sodium nitride |
Na+ Na+ Na+ |
N3- | 3:1 | Na3N |
| Magnesium oxide | Mg2+ | O2- | 1:1 | MgO |
| Aluminum nitrde | Al3+ | N3- | 1:1 | AlN |
| Calcium nitride |
Ca2+ Ca2+ Ca2+ |
N3- N3- |
3:2 | Ca3N2 |
Click on the ionic compound link to show or hide each chemical formula.
Chemical Formula Table
|
Na+
|
K+
|
Mg2+
|
Ca2+
|
Al3+
|
|
|---|---|---|---|---|---|
| NaCl sodium chloride |
KCl potassium chloride |
MgCl2 magnesium chloride |
CaCl2 calcium chloride |
AlCl3 aluminum chloride |
Cl-
|
| Na2O sodium oxide |
K2O potassium oxide |
MgO magnesium oxide |
CaO calcium oxide |
Al2O3 aluminum oxide |
O2-
|
| NaBr sodium bromide |
KBr potassium bromide |
MgBr2 magnesium bromide |
CaBr2 calcium bromide |
AlBr3 aluminum bromide |
Br-
|
| Na2S sodium sulfide |
K2S potassium sulfide |
MgS magnesium sulfide |
CaS calcium sulfide |
Al2S3 aluminum sulfide |
S2-
|
| Na3P sodium phosphide |
K3P potassium phosphide |
Mg3P2 magnesium phosphide |
Ca3P2 calcium phosphide |
AlP aluminum phosphide |
P3-
|