What represents the formula of an ionic compound?

The formula of an ionic compound represents the ratio of the ions present in the compound.

In more detail, an ionic compound is made up of positively charged ions, known as cations, and negatively charged ions, known as anions. These ions come together to form a neutral compound, and the formula of this compound shows the ratio of the different ions present. For example, in sodium chloride (NaCl), the formula indicates that there is one sodium ion (Na+) for every chloride ion (Cl-).

The formula of an ionic compound is determined by the charges of the ions. The overall charge of an ionic compound must be neutral, so the charges of the ions must balance out. For instance, in magnesium chloride (MgCl2), the magnesium ion (Mg2+) has a charge of +2, while the chloride ion (Cl-) has a charge of -1. Therefore, two chloride ions are needed to balance the charge of one magnesium ion, resulting in the formula MgCl2.

The formula of an ionic compound also gives us information about its structure. Ionic compounds form a special type of structure known as a crystal lattice, where the ions are arranged in a repeating pattern. The formula tells us the simplest ratio of ions in this lattice. For example, in the compound aluminium oxide (Al2O3), the formula tells us that in the crystal lattice, there are two aluminium ions for every three oxygen ions.

In summary, the formula of an ionic compound represents the ratio of the ions present in the compound, determined by their charges, and gives us information about the structure of the compound.