Chemical Formula for Salts

Salts are chemical compounds that are formed through the reaction of bases and acids.

Most of us equate the term 'salts', which is a class of numerous compounds, with 'salt', which is a condiment. However, in scientific terms, the terms are distinct, and should be treated as such. In chemistry, salts are categorized as a group of chemicals with their own features and properties.

The formulae for particular salts derive from the nature of the anions and cations present in the salt.

To know a chemical formula, it's necessary that one should be aware of various cations and anions that are necessary in the formation of the compounds. The table given below gives various cations/anions and their symbols along with the charge on them.

Anions are ions that have gained an extra electron, and thus have a net negative charge. Conversely, cations are ions that have lost an electron, and have a net positive charge.

Ion Name : Symbol

Aluminum : Al3+
Ammonium : NH+
Arsenic(III) : Ar3+
Arsenic(V) : Ar5+
Barium : Ba2+
Beryllium : Be2+
Bismuth(III) : Bi3+
Bismuth(V) : Bi5+
Cadmium : Cd2+

Chromium(III) : Cr3+
Cobalt(II) : Co2+
Copper(I) : Cu+
Hydrogen : H+
Iron (II) : Fe2+
Tin(II) : Sn2+
Iron (III) : Fe3+
Lead(II) : Pb2+
Lead(IV) : Pb4+
Silver : Ag2+

Zinc : Zn2+
Mercury(I) : Hg22+
Mercury(II) : Hg2+
Gold(I) : Au+
Gold(III) : Au3+
Tin(IV) : Sn4+
Sodium : Na+
Lithium : Li+
Potassium : K+
Rubidium : Rb+
Cesium : Cs+

Ion Name : Symbol

Acetate : CH3COO-
Borate : BO33-
Bromate : BrO3-
Bromide : Br-
Carbonate : CO32-
Chloride : Cl-
Chlorate : ClO3-
Chlorite : ClO2-
Hypochlorite : ClO-

Chlormate : CrO42-
Cyanide : CN-
Iodate : IO3-
Dichromate : Cr2O72-
Dihydrogen Phosphate : H2PO4-
Ferricyanide : Fe(CN)64-
Fluoride : F-
Iodide : I-
Oxide : O2-
Nitrate : NO3-

Nitrite : NO2-
Permanganate : MnO4-
Hydroxide : OH-
Peroxide : O22-
Perchlorate : ClO4-
Ferrocyanide : Fe(CN)63-
Amide : NH2-
Hydrogen Carbonate : HCO3-
Sulfate : SO42-
Sulfite : SO3-
Hydrogen Sulfate : HSO4

As mentioned earlier, using these symbols, we can know the chemical formula for various salts. The steps to derive its formula have been discussed further.

• Determine the cations and anions in the salt formula. Every salt is made of cations and anions.

• The formula for chemical salt is always written with the element of the cation preceding the element of the anion, with a '-ide' or '-ate' suffix added to the latter.
• A salt is always neutral, which means total charge from the anions and cations must be zero. To do this while formulating, we have to cross multiply.

To understand the procedure better, we must study some examples.

Example #1: Determine the Formula for Sodium Sulfate

This salt consists of sodium (cation) and sulfate ions (anion).

Sodium Ion → Na⁺
Sulfate Ion → SO₄^2-

For convenience in understanding, we will use square brackets to separate cations, anions and the element. Therefore,

[Na]⁺ [SO₄]^2-

[Na]_2- [SO₄]₊ (Remember cross multiply rule. So cross multiply charges on respective ions)

Hence, Na₂SO₄ (Remove square brackets and charges)

Example #2: Determine the formula for Barium Oxide

This salt consists of barium (cation) and oxide (anions) ions.

Barium → Ba²⁺
Oxide → O^2-

[Ba]²⁺ [O]^2-

Hence, BaO

Once you are aware of cations and anions, it's very easy to come up with the chemical formula for any salt.