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Chemical Formula for Salts

Chemical Formula for Salts
Chemical formula for a salt can be deciphered by knowing which chemical compounds must have reacted to form it. Read on to know more...
Kundan Pandey
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.
Cations and Anions
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.
Cations Anions
Ion Name Symbol Ion Name Symbol
Aluminum Al3+ Acetate CH3COO-
Ammonium NH+ Borate BO33-
Arsenic(III) Ar3+ Bromate BrO3-
Arsenic(V) Ar5+ Bromide Br-
Barium Ba2+ Carbonate CO32-
Beryllium Be2+ Chloride Cl-
Bismuth(III) Bi3+ Chlorate ClO3-
Bismuth(V) Bi5+ Chlorite ClO2-
Cadmium Cd2+ Hypochlorite ClO-
Chromium(III) Cr3+ Chlormate CrO42-
Cobalt(II) Co2+ Cyanide CN-
Copper(I) Cu+ Iodate IO3-
Hydrogen H+ Dichromate Cr2O72-
Iron (II) Fe2+ Dihydrogen Phosphate H2PO4-
Tin(II) Sn2+ Ferricyanide Fe(CN)64-
Iron (III) Fe3+ Fluoride F-
Lead(II) Pb2+ Iodide I-
Lead(IV) Pb4+ Oxide O2-
Silver Ag2+ Nitrate NO3-
Zinc Zn2+ Nitrite NO2-
Mercury(I) Hg22+ Permanganate MnO4-
Mercury(II) Hg2+ Hydroxide OH-
Gold(I) Au+ Peroxide O22-
Gold(III) Au3+ Perchlorate ClO4-
Tin(IV) Sn4+ Ferrocyanide Fe(CN)63-
Sodium Na+ Amide NH2-
Lithium Li+ Hydrogen Carbonate HCO3-
Potassium K+ Sulfate SO42-
Rubidium Rb+ Sulfite SO3-
Cesium Cs+ Hydrogen Sulfate HSO4-
Steps to Derive Formula
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 → SO42-
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 → O2-
[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.