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Chemical Formula

Last Updated : 02 Apr, 2024
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Chemical formula is a way to describe chemical ratios of atoms that make up a specific chemical compound or molecule in chemistry. Chemical element symbols, numbers, and sometimes other symbols, such as parentheses, dashes, brackets, commas, plus (+), and minus (-) signs, are used to represent the chemical elements, atoms, or ions. A chemical substance that contains atoms from at least two different elements is referred to be a chemical compound. Chemical compounds and molecules both contain many atoms, but unlike chemical compounds, a molecule can just be made up of atoms from the same element.

In this article, we have covered, Definition of Chemical Formula, Importance of Chemical Formula, Types of Chemical Formulae, and others in detail.

What is Chemical Formula?

A chemical formula is a representation of a substance’s molecular composition in terms of the symbols representing the components that make up the molecule. A molecular formula is another name for a chemical formula.

An element’s or a compound’s chemical formula can be used. A chemical formula is a technique of presenting information on the chemical proportions of atoms that make up a chemical compound or molecule using chemical element symbols, numbers, and other symbols like parentheses, dashes, brackets, and commas.

Importance of Chemical Formula

The importance of Chemical Formulas can be understood as,

  • Compound’s name is represented by a formula.
  • Names of all the elements in the molecule are given in formulae.
  • Number of atoms of each element contained in a molecule is given by formulae.
  • One molecule of a compound is represented by a formula.
  • Formulae denote a definite mass of a substance.

Types of Chemical Formulae

There are different types of chemical formulae based on the composition of chemical compounds:

Molecular Formula

Amount of elements in a substance can be determined from its molecular formula. The periodic table’s symbols are used to represent the elements in molecular formulae, and a subscript is used to indicate how many atoms of each element are present in the molecule.


  • Molecular formula of Urea is CH4N2O which gives exact number of constituent atoms (i.e Carbon, Hydrogen and Nitrogen in one Urea molecule
  • Molecular formula of Acetic Acid is CH3COOH
  • Molecular formula of Glucose is C6H12O6

Empirical Formula

Ratio of the elements present in a chemical compound is represented by its empirical formula. Usually, empirical formulas are developed by the evaluation of experimental data.


  • Empirical formula of Urea is CH4N2O
  • Empirical formula of Acetic Acid is CH2O
  • Empirical formula of Glucose is CH2O

Structural Formula

Structural formula of a chemical compound gives understanding of the arrangement of the atoms in the molecule.


Structural formula of Urea is shown below,

Structural Formula of Urea

Structural formula of Acetic Acid is shown below,

Structural formula of Acetic Acid

How to Write Chemical Formula?

A binary compound is composed of two different elements only. Formulae of binary compounds can be written with the help of valency of elements since both types of atoms forming the compound must lose, gain or share the same number of electrons.

Points to be considered to write the molecular formula

  • Determine the valency of the elements present in the compound.
  • Write the chemical formula such that the sums of the valency of the two elements are equal. Do this by determining the lowest common multiple of the two valency.
  • Always place metals first in the formula.

Chemical Formula of Rust

Elements present in Rust are Iron and Oxygen. Then, 


Iron, Fe (26)

Oxygen, O (8)




Lowest common multiple of valency is 6. Therefore,

Fe = 2 × 3 = 6

O = 3 × 2 = 6

This implies that the chemical formula is Fe2O3

Chemical Formula of Aluminium Oxide

The elements present in Aluminium Oxide are Aluminium and Oxygen. Then, 


Aluminium, Al (13)

Oxygen, O (8)




The lowest common multiple of valency is 6. Therefore,

Al = 2 × 3 = 6

O = 3 × 2 = 6

This implies that the chemical formula is Al2O3

Chemical Formula of Methane

Elements present in Methane are Carbon and Hydrogen. Then, 

Symbol  Carbon, C (6) Hydrogen, H (1)



Lowest common multiple of valency is 4. Therefore,

C = 1 × 4

H = 4 × 1

This implies that the chemical formula is CH4

Chemical Formula of Sodium Chloride

Elements present in Sodium Chloride are Carbon and Hydrogen. Then, 

Symbol  Sodium, Na (11) Chlorine, Cl (17)



Lowest common multiple of valency is 4. Therefore,

Na = 1

Cl = 1

This implies that the chemical formula is CH4

Chemical Formula of Calcium Oxide

Elements present in Calcium Oxide are Calcium and Oxygen. Then,

Symbol  Calcium, Ca (20) Oxygen, O (8)



Lowest common multiple of valency is 2. Therefore.

Ca = 1 × 2

O = 1 × 2

This implies that the chemical formula is CaO.

Chemical Formula of Some Common Compounds

Chemical Formula of some common compounds are:

Chemical Formula Table

The table given below gives the chemical symbol and molecular weight of some common compounds

Compound Name

Chemical Symbol

Molecular Weight (g/mol)

Acetic acid CH3COOH 60.052
Hydrochloric acid HCl 36.458
Sulfuric acid H2SO4 ‎98.072
Ammonia NH3 17.031
Nitric acid HNO3 63.012
Phosphoric acid H3PO4 97.994
Sodium phosphate Na3PO4 119.976
Calcium carbonate CaCO3 100.086
Ammonium sulfate (NH4)2SO4 132.134
Carbonic acid H2CO3 62.024
Sodium bicarbonate NaHCO3 84.0066
Sodium hydroxide NaOH 39.997
Calcium hydroxide Ca(OH)2 74.092
Ethanol C2H5OH 46.069
Hydrobromic acid HBr 80.912
Nitrous acid HNO2 ‎47.013
Potassium hydroxide KOH 56.11
Silver nitrate AgNO3 169.872
Sodium carbonate Na2CO3 105.988
Sodium chloride NaCl 58.44
Magnesium hydroxide Mg(OH)2 58.319
Methane CH4 16.043
Nitrogen dioxide NO2 30.006
Sodium nitrate NaNO3 84.994
Aluminium sulfate Al2(SO4)3 342.15
Aluminium oxide Al2O3 101.96
Ammonium nitrate NH4NO3 80.043
Ammonium phosphate (NH4)3PO4 132.056
Barium hydroxide Ba(OH)2 171.341
Carbon tetrachloride CCl4 153.811
Citric acid C6H8O7 192.123
Hydrocyanic acid HCN ‎27.026
Salicylic Acid C7H6O3 138.121
Hydroiodic acid HI 127.91
Hypochlorous acid HClO 52.457
Magnesium phosphate Mg3(PO4)2 262.855
Sodium acetate C2H3NaO2 82.0343
Sodium sulfate Na2SO4 ‎142.036
Sucrose C12H22O11 342.2965
Potassium nitrate KNO3 101.102
Ammonium bicarbonate NH4HCO3 96.086
Ammonium chloride NH4Cl 53.489
Ammonium hydroxide NH4OH 35.046
Calcium nitrate Ca(NO3)2 164.088
Calcium oxide CaO 56.0774
Carbon monoxide CO 28.01
Phenol C6H6O 94.11
Hydrogen peroxide H2O2 34.0147
Magnesium chloride MgCl2 95.211
Potassium chloride KCl 74.5513
Potassium iodide KI 166.0028
Sulfur dioxide SO2 64.066
Calcium acetate C4H6O4Ca 158.17
Iron oxide Fe2O3 159.69
Potassium carbonate K2CO3 138.205
Silver chloride AgCl ‎143.318
Sodium iodide NaI 149.894
Sodium oxide Na2O 61.9789
Zinc nitrate Zn(NO3)2 189.388
Magnesium nitrate Mg(NO3)2 148.313
Silicon dioxide SiO2 60.083
Ammonium acetate C2H3O2NH4 77.083
Benzene C6H6 78.11
Methyl Ethyl Ketone C4H8O 72.107
Trichloroacetic acid C2HCl3O2 163.38
Magnesium sulfate MgSO4 120.361
Methanol CH3OH 32.04
Sodium sulfite Na2SO3 126.043
Sulfur trioxide SO3 80.057
Aluminium phosphate AlPO4 121.951
Dinitrogen monoxide N2O 44.013
Potassium dichromate K2Cr2O7 294.185
Sodium bromide NaBr 102.894
Sodium hypochlorite NaClO 74.439
Zinc acetate Zn(CH3COO)2(H2O)2 183.48
Zinc chloride ZnCl2 136.286
Zinc hydroxide Zn(OH)2 99.424
Magnesium carbonate MgCO3 84.313
Potassium chlorate KClO3 122.545
Hydrazine N2H4 32.0452
Maleic acid C4H4O4 116.072
Dichloromethane CH2Cl2 84.93
Potassium chromate CrK2O4 194.189
Zinc sulfate ZnSO4 161.436
Aluminum Al 26.982
Perchloric acid HClO4 100.46
Potassium Bromide KBr 119.002
Chromic acid H2CrO4 118.01
Methyl acetate C3H6O2 74.079
Hexane C6H14 86.18
Manganese dioxide MnO2 86.9368
Lactic acid C3H6O3 90.078
Lithium hydroxide LiOH 23.95
Phosphorus pentachloride PCl5 208.24
Potassium oxide K2O 94.2 
Monopotassium phosphate KH2PO4 136.084
Sodium fluoride NaF 41.98817
Sodium nitrite NaNO2 68.9953
Barium carbonate BaCO3 197.34
Calcium Iodide CaI2 293.887
Lithium oxide Li2O 29.88
Potassium Permanganate KMnO4 158.034
Silver phosphate Ag3PO4 418.58
Ammonium bromide NH4Br 97.943
Calcium phosphate Ca3(PO4)2 310.18
Ammonium carbonate (NH4)2CO3 96.086
Barium chloride BaCl2 208.23
Magnesium iodide MgI2 278.1139
Ozone O3 48
Potassium cyanide KCN 65.12
Silver oxide Ag2O 231.735
Sodium chromate Na2CrO4 161.97
Sodium peroxide Na2O2 77.98
Zinc carbonate ZnCO3 125.388
Zinc phosphate Zn3(PO4)2 386.11
Zinc sulfide ZnS 97.474
Boric acid H3BO3 61.83
Potassium bicarbonate KHCO3 100.114
Potassium hypochlorite KClO 90.55
Potassium nitrite KNO2 85.103
Ammonium iodide NH4I 144.94
Ammonium nitrite NH4NO2 64.06
Ammonium oxide (NH4)2O 52.0763
Barium bromide BaBr2 297.14
Barium iodide BaI2 391.136
Dinitrogen trioxide N2O3 76.01
Ethylene glycol C2H6O2 62.07
Nickel sulfate NiSO4 154.75
Lithium chloride LiCl 42.394
Potassium fluoride KF 58.0967
Potassium sulfite K2SO3 158.26
Silver carbonate Ag2CO3 275.7453
Sodium cyanide NaCN 49.0072
Sodium nitride Na3N 82.976
Strontium chloride SrCl2 158.52
Urea CH4N2O ‎60.056
Bleach NaClO ‎74.439
Lithium bromide LiBr 86.844
Aluminium fluoride AlF3 83.9767
Barium fluoride BaF2 175.34
Copper (II) carbonate CuCO3 123.55
Fluorine F 18.998403
Lithium phosphate Li3PO4 115.79
Lead Iodide PbI2 461.01
Lithium iodide LiI 133.844
Magnesium oxide MgO 40.3044
Sodium dichromate Na2Cr2O7 261.97l
Tartaric acid C4H6O6 150.087
Zinc iodide ZnI2 319.22
Bromine Br 54.9380
Aluminum bromide AlBr3 266.69
Sodium Percarbonate C2H6Na4O12 157.01
Nickel acetate C4H6O4Ni 178.797
Acetaldehyde C2H4O 44.05
Copper sulfate CuSO4 159.609
Calcium Chloride CaCl2 110.98
Sodium Chlorate NaClO3 106.44
Potassium Iodate KIO3 214.001
Lead Acetate Pb(C2H3O2)2 325.29
Formaldehyde CH2O 30.031
Formic Acid HCOOH 46.03
Sulfur Hexafluoride SF6 146.06
Ethane C2H6 30.07
Dinitrogen Pentoxide N2O5 30.07
Phosphorous Acid H3PO3 82
Aluminium hydroxide Al(OH)3 78.00
Potassium acetate CH3CO2K 98.142
Barium oxide BaO 153.326
Copper(I) Oxide Cu2O 143.09
Copper Hydroxide Cu(OH)2 97.561
Ethylene C2H4 28.054
Acetylene C2H2 26.038
Chromic Oxide Cr2O3 151.9904
Sodium bisulfate NaHSO4 120.06
Copper (II) chloride CuCl2 134.45
Mercuric chloride HgCl2 271.52
Tin (II) chloride SnCl2 189.60
Propane C3H8 44.097
Lead (IV) oxide PbO2 239.1988

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FAQs on Chemical Formula

Define Chemical Formula?

The term chemical formula is used to define the chemical composition of any compound. It tells us about the elements a compound has, it also tells us about the ratio in which these elements combine.

What is Chemical Formula of Ozone?

Chemical formula of ozone is O3. In ozone three oxygen atoms are combined with each other.

What is Chemical Formula of Rust?

Chemical formula of rust is Fe2O3. Its scientific name is Ferric Oxide.

What is Chemical Formula of Baking Soda?

Chemical formula of baking soda is NaHCO3. Its scientific name is sodium bicarbonate.

What is Chemical Formula of Bleaching Powder?

Chemical formula of bleaching powder is CaOCl2. Its scientific name is calcium oxychloride.

What is Chemical Formula of Washing Soda?

Chemical formula of washing soda is NaCO3. Its scientific name is sodium carbonate.

What is Chemical Formula of Calcium Carbonate?

Chemical formula of calcium carbonate is CaCO3. The common name of calcium carbonate is Chalk.

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