Ionic compound formula

What are ionic compounds?

Ionic compounds are neutral compounds consist of cations and anions. All ionic compounds have a particular ionic unit with a specific charge. The amount of cation and anion in the ionic compound is always equal.  The chemical equation of an ionic compound reflects the ionic units and the ratio of cation and anions.

Ionic compound formula

Chemical formulas of ionic compounds are not complicated to write. Write the cation symbol followed by anion symbol. Then, find the lowest multiple of the ions to make the compound neutral. The ionic compound consists of charged ions but the overall compound and its formula are electrically neutral. In other words,

The total number of Positive charge on the cation = The total number of Negative charge of the anion

Ionic compounds usually consist of a combination of metals and nonmetals. These are the guidelines to ensure uniformity in writing the ionic compound formula.

  1.    The cation is always placed before anion.
  2.    Polyatomic ion formula is always written as a unit.
  3.    Polyatomic ions are placed in parentheses with the following subscript to represent different ratios from 1:1.

Example 1

Determine the chemical formula of the ionic compound Calcium Chloride.


The names of cations and anions identify the chemical formulas along with changes of each ion. The charges indicate the ion ratio that needs to appear in the chemical formula.

Calcium chloride contains Ca+ of Group 2 and Cl of Group 17. That’s the reason there must be two anions for every cation. Therefore, the chemical formula of calcium chloride is CaCl2.


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