100 Important Chemical Formulas - Names, List and Uses

Chemical formulas provide a compact way to represent substances, elements and compounds. A formula tells you which elements are present and how their atoms or ions combine. For example, H₂O contains two hydrogen atoms and one oxygen atom, while CO₂ contains one carbon atom and two oxygen atoms.

Learning the most important chemical formulas helps students understand chemical equations, reactions, valency, molar mass and compound naming. These formulas often appear in school examinations, competitive tests, laboratory work and everyday science. Common examples include NaCl for common salt, HCl for hydrochloric acid, NaOH for caustic soda and CaCO₃ for limestone.

The reference chart contains 100 common formulas, but a few entries require correction. Nitrogen gas is N₂, not Na. Anhydrous copper sulfate is CuSO₄, not CuO. Copper(II) oxide is CuO, not FeO. Sodium hydroxide is called caustic soda, not caustic acid. These corrections have been included in the complete list below.

This guide covers the 100 most important chemical formulas, their correct names, formula types, common uses and easy memorization methods. It uses both spellings, such as sulfate and sulphate, where students often encounter regional variations.

What Is a Chemical Formula?

A chemical formula uses element symbols and numbers to show the composition of a substance. It identifies the elements present and gives their relative proportions.

IUPAC defines a molecular formula as a formula consistent with the relative molecular mass or structure of a substance made of discrete molecules. An empirical formula gives the simplest whole-number ratio of the elements in a substance.

For example:

• H₂O represents water.
• NaCl represents sodium chloride.
• H₂SO₄ represents sulfuric acid.
• Ca(OH)₂ represents calcium hydroxide.
• CuSO₄·5H₂O represents hydrated copper sulfate.

Main Types of Chemical Formulas

Formula Type	Meaning	Example
Molecular formula	Shows the actual number of atoms in a molecule	C₆H₁₂O₆
Empirical formula	Shows the simplest ratio of atoms	CH₂O for glucose
Condensed formula	Shows groups of atoms in a compact form	CH₃COOH
Structural formula	Shows how atoms connect	H–O–H
Formula unit	Represents the simplest ion ratio in an ionic compound	NaCl
Hydrated formula	Shows water present in a crystal	CuSO₄·5H₂O

A hydrate contains water molecules within its crystal structure. The centered dot separates the compound from its water of crystallization.

Important Corrections in the Reference Chemical Formula Chart

The supplied chart contains several useful formulas, but these five entries need correction:

• Nitrogen gas: The correct formula is N₂, not Na. Na represents sodium.
• Caustic soda: NaOH is sodium hydroxide or caustic soda. It is not called caustic acid.
• Anhydrous copper sulfate: The correct formula is CuSO₄, not CuO.
• Copper(II) oxide: The correct formula is CuO, not FeO. FeO represents iron(II) oxide.
• Phosphorus pentoxide: Its molecular formula is P₄O₁₀, while P₂O₅ is its empirical formula. P₂O₃ does not represent phosphorus pentoxide.

List of 100 Most Important Chemical Formulas

Chemical Formulas 1 to 20

No.	Chemical Name	Correct Formula
1	Water	H₂O
2	Common salt, sodium chloride	NaCl
3	Carbon dioxide	CO₂
4	Hydrogen gas	H₂
5	Oxygen gas	O₂
6	Nitrogen gas	N₂
7	Hydrochloric acid	HCl
8	Sulfuric acid, sulphuric acid	H₂SO₄
9	Nitric acid	HNO₃
10	Sodium hydroxide, caustic soda	NaOH
11	Potassium hydroxide, caustic potash	KOH
12	Ammonia	NH₃
13	Calcium carbonate, limestone	CaCO₃
14	Calcium hydroxide, slaked lime	Ca(OH)₂
15	Calcium oxide, quicklime	CaO
16	Methane, marsh gas	CH₄
17	Glucose	C₆H₁₂O₆
18	Sucrose, table sugar	C₁₂H₂₂O₁₁
19	Ethanol, ethyl alcohol	C₂H₅OH
20	Acetic acid, ethanoic acid	CH₃COOH

Chemical Formulas 21 to 40

No.	Chemical Name	Correct Formula
21	Baking soda, sodium bicarbonate	NaHCO₃
22	Washing soda	Na₂CO₃·10H₂O
23	Bleaching powder	Ca(OCl)Cl, often written CaOCl₂
24	Plaster of Paris	CaSO₄·½H₂O
25	Gypsum	CaSO₄·2H₂O
26	Potassium permanganate	KMnO₄
27	Potassium dichromate	K₂Cr₂O₇
28	Hydrogen peroxide	H₂O₂
29	Carbon monoxide	CO
30	Sulfur dioxide	SO₂
31	Sulfur trioxide	SO₃
32	Hydrogen sulfide	H₂S
33	Nitrous oxide, laughing gas	N₂O
34	Nitric oxide, nitrogen monoxide	NO
35	Phosphoric acid	H₃PO₄
36	Nitrogen dioxide	NO₂
37	Urea	CO(NH₂)₂
38	Chloroform	CHCl₃
39	Carbon tetrachloride	CCl₄
40	Benzene	C₆H₆

Chemical Formulas 41 to 60

No.	Chemical Name	Correct Formula
41	Toluene, methylbenzene	C₆H₅CH₃
42	Acetylene, ethyne	C₂H₂
43	Ethylene, ethene	C₂H₄
44	Formaldehyde, methanal	HCHO
45	Acetaldehyde, ethanal	CH₃CHO
46	Acetone, propanone	CH₃COCH₃
47	Ozone	O₃
48	Blue vitriol, copper sulfate pentahydrate	CuSO₄·5H₂O
49	Green vitriol, ferrous sulfate heptahydrate	FeSO₄·7H₂O
50	Ferric chloride, iron(III) chloride	FeCl₃
51	Silver nitrate	AgNO₃
52	Zinc sulfate	ZnSO₄
53	Alumina, aluminium oxide	Al₂O₃
54	Ammonium chloride, sal ammoniac	NH₄Cl
55	Sodium thiosulfate, hypo	Na₂S₂O₃·5H₂O
56	Borax	Na₂B₄O₇·10H₂O
57	Potash alum	KAl(SO₄)₂·12H₂O
58	Calcium carbide	CaC₂
59	Magnesium hydroxide, milk of magnesia	Mg(OH)₂
60	Potassium chlorate	KClO₃

Chemical Formulas 61 to 80

No.	Chemical Name	Correct Formula
61	Magnesia, magnesium oxide	MgO
62	Anhydrous copper sulfate	CuSO₄
63	Copper(II) oxide, cupric oxide	CuO
64	Ferric oxide, iron(III) oxide	Fe₂O₃
65	Zinc oxide	ZnO
66	Silica, silicon dioxide	SiO₂
67	Sodium oxide	Na₂O
68	Potassium chloride	KCl
69	Sodium sulfate	Na₂SO₄
70	Sodium nitrate	NaNO₃
71	Potassium nitrate, saltpetre	KNO₃
72	Calcium chloride	CaCl₂
73	Magnesium sulfate, Epsom salt	MgSO₄·7H₂O
74	Ammonium sulfate	(NH₄)₂SO₄
75	Ammonium nitrate	NH₄NO₃
76	Aqueous ammonia, often written ammonium hydroxide	NH₃(aq), commonly NH₄OH
77	Sodium sulfide	Na₂S
78	Sodium sulfite	Na₂SO₃
79	Calcium sulfate	CaSO₄
80	Barium sulfate	BaSO₄

Chemical Formulas 81 to 100

No.	Chemical Name	Correct Formula
81	Barium chloride	BaCl₂
82	Silver chloride	AgCl
83	Silver bromide	AgBr
84	Silver iodide	AgI
85	Lead(II) nitrate	Pb(NO₃)₂
86	Lead(II) iodide	PbI₂
87	Copper(II) chloride	CuCl₂
88	Magnesium chloride	MgCl₂
89	Phosphorus pentoxide	P₄O₁₀, empirical formula P₂O₅
90	Phosphine	PH₃
91	Sulfurous acid	H₂SO₃
92	Carbonic acid	H₂CO₃
93	Boric acid	H₃BO₃
94	Hydrofluoric acid	HF
95	Hydrobromic acid	HBr
96	Hydroiodic acid	HI
97	Calcium phosphate	Ca₃(PO₄)₂
98	Magnesium carbonate	MgCO₃
99	Trisodium phosphate	Na₃PO₄
100	Potassium perchlorate	KClO₄

How to Read a Chemical Formula

Element Symbols

Every chemical element has a unique symbol. The first letter always uses uppercase, while a second letter uses lowercase.

Examples:

• H means hydrogen.
• O means oxygen.
• Na means sodium.
• Cl means chlorine.
• Ca means calcium.
• Fe means iron.

Writing NA instead of Na changes the notation and makes the formula incorrect.

Subscripts

A subscript shows how many atoms of an element appear in one molecule or formula unit.

Example: H₂O

• H₂ means two hydrogen atoms.
• O without a subscript means one oxygen atom.
• One water molecule contains three atoms in total.

Example: C₆H₁₂O₆

One glucose molecule contains:

• 6 carbon atoms
• 12 hydrogen atoms
• 6 oxygen atoms
• 24 atoms in total

Parentheses

Parentheses group atoms or polyatomic ions. A subscript outside the parentheses applies to every atom inside them.

Example: Ca(OH)₂

Calcium hydroxide contains:

• 1 calcium atom
• 2 oxygen atoms
• 2 hydrogen atoms

The subscript 2 multiplies both O and H in the hydroxide group.

Hydration Dot

A centered dot shows water molecules held within a crystal.

Example: CuSO₄·5H₂O

Copper sulfate pentahydrate contains one copper sulfate formula unit and five water molecules. Heating removes the water and produces anhydrous CuSO₄.

Other common hydrates include:

• Washing soda, Na₂CO₃·10H₂O
• Gypsum, CaSO₄·2H₂O
• Epsom salt, MgSO₄·7H₂O
• Potash alum, KAl(SO₄)₂·12H₂O

Common Ions Used in Chemical Formulas

Learning common ions reduces the need to memorize every formula separately.

Ion Name	Formula	Charge
Ammonium	NH₄⁺	+1
Hydroxide	OH⁻	−1
Nitrate	NO₃⁻	−1
Bicarbonate	HCO₃⁻	−1
Permanganate	MnO₄⁻	−1
Carbonate	CO₃²⁻	−2
Sulfate	SO₄²⁻	−2
Sulfite	SO₃²⁻	−2
Dichromate	Cr₂O₇²⁻	−2
Phosphate	PO₄³⁻	−3

Sulfate vs Sulfite

Students often confuse these two ions:

• Sulfate: SO₄²⁻
• Sulfite: SO₃²⁻

The “ate” ion contains more oxygen than the related “ite” ion.

Examples:

• Sodium sulfate is Na₂SO₄.
• Sodium sulfite is Na₂SO₃.

Nitrate vs Nitrite

• Nitrate: NO₃⁻
• Nitrite: NO₂⁻

Examples:

• Sodium nitrate is NaNO₃.
• Sodium nitrite is NaNO₂.

Common Chemical Formulas and Everyday Uses

Compound	Formula	Common Context
Water	H₂O	Drinking, cleaning and biological processes
Sodium chloride	NaCl	Food, saline solutions and chemical production
Carbon dioxide	CO₂	Photosynthesis, carbonation and fire extinguishers
Sodium bicarbonate	NaHCO₃	Baking, cleaning and antacid products
Calcium carbonate	CaCO₃	Limestone, cement and antacid products
Calcium hydroxide	Ca(OH)₂	Whitewashing and water treatment
Ethanol	C₂H₅OH	Solvents, fuels and disinfectant products
Acetic acid	CH₃COOH	Main acidic component of vinegar
Hydrogen peroxide	H₂O₂	Bleaching and disinfecting products
Magnesium hydroxide	Mg(OH)₂	Milk of magnesia preparations
Silicon dioxide	SiO₂	Sand, glass and ceramics
Barium sulfate	BaSO₄	Medical imaging contrast material

Some listed chemicals are corrosive, poisonous or strong oxidizers. Students should treat the list as educational material and never handle laboratory chemicals without proper supervision.

How to Memorize Chemical Formulas Faster

1. Learn Element Symbols First

Start with common symbols such as H, O, N, C, Na, K, Ca, Mg, Fe, Cu, Zn, Ag and Cl. Formula learning becomes easier once you recognize every symbol instantly.

2. Memorize Polyatomic Ions

Focus on nitrate, sulfate, carbonate, hydroxide, phosphate and ammonium. Many compounds use the same ions in different combinations.

For example:

• Sodium sulfate: Na₂SO₄
• Potassium sulfate: K₂SO₄
• Ammonium sulfate: (NH₄)₂SO₄

3. Group Compounds by Category

Study formulas in small groups:

• Acids
• Bases
• Salts
• Gases
• Organic compounds
• Metal oxides
• Hydrated salts

This method creates clear associations between names and formulas.

4. Use Valency to Build Formulas

Do not rely only on memorization. Use ionic charges to construct formulas.

Calcium has a +2 charge, while chloride has a −1 charge. Two chloride ions balance one calcium ion, producing CaCl₂.

5. Write Formulas Daily

Read the compound name, cover the formula and write it from memory. Check your answer immediately and repeat incorrect entries.

A short daily revision session works better than one long session before an examination.

6. Use Two-Way Flashcards

Write the compound name on one side and its formula on the other. Practice in both directions:

• Name to formula
• Formula to name

This approach prepares you for different question formats.

Common Mistakes to Avoid

• Do not confuse Na with nitrogen. Na means sodium, while nitrogen gas is N₂.
• Do not change uppercase and lowercase letters. CO means carbon monoxide, while Co represents cobalt.
• Do not ignore parentheses. CaOH₂ is not the correct way to write Ca(OH)₂.
• Do not confuse coefficients with subscripts.
• Do not write Na₂CO₃ for washing soda without including its ten water molecules.
• Do not confuse CuSO₄ with CuO.
• Do not use P₂O₃ for phosphorus pentoxide.
• Do not call NaOH an acid. Sodium hydroxide is a strong base.
• Do not confuse sulfate, SO₄²⁻, with sulfite, SO₃²⁻.
• Do not confuse nitrate, NO₃⁻, with nitrite, NO₂⁻.

Why These 100 Chemical Formulas Matter

These formulas form a foundation for chemistry. They help students write balanced equations, calculate molar masses, identify reaction products and understand acids, bases, salts and organic compounds.

The list supports school chemistry, laboratory revision and competitive examination preparation. It also connects textbook concepts with substances found in food, medicines, construction materials, agriculture and industry.

FAQs

1. What is a chemical formula?

A chemical formula represents the elemental composition of a substance. It uses element symbols and subscripts to show which elements are present and their relative numbers. For example, H₂O shows that water contains hydrogen and oxygen in a 2:1 atomic ratio.

2. What is the difference between a molecular formula and an empirical formula?

A molecular formula shows the actual number of each type of atom in a molecule. An empirical formula gives the simplest whole-number ratio of those atoms. Glucose has the molecular formula C₆H₁₂O₆ and the empirical formula CH₂O.

3. What is the chemical formula of water?

The chemical formula of water is H₂O. Each molecule contains two hydrogen atoms and one oxygen atom. The subscript 2 applies only to hydrogen.

4. What is the formula of common salt?

The formula of common salt is NaCl. It consists of sodium ions and chloride ions in a 1:1 ratio. Its chemical name is sodium chloride.

5. What is the correct formula of nitrogen gas?

The correct formula of nitrogen gas is N₂. Nitrogen normally exists as a diatomic molecule under ordinary conditions. Na is the chemical symbol for sodium, not nitrogen.

6. Is NaOH caustic acid or caustic soda?

NaOH is sodium hydroxide, commonly called caustic soda. It is a strong base rather than an acid. Caustic potash refers to potassium hydroxide, KOH.

7. What are the formulas of blue vitriol and green vitriol?

Blue vitriol is copper sulfate pentahydrate, CuSO₄·5H₂O. Green vitriol is ferrous sulfate heptahydrate, FeSO₄·7H₂O. Both compounds contain water of crystallization.

8. Why is phosphorus pentoxide written as P₂O₅ or P₄O₁₀?

P₄O₁₀ represents the molecular formula of phosphorus pentoxide. P₂O₅ represents its simplest empirical formula. Both forms appear in textbooks, but P₂O₃ is not the formula of phosphorus pentoxide.

9. What does the dot in a hydrated formula mean?

The centered dot shows water molecules incorporated into a crystalline compound. CuSO₄·5H₂O contains five water molecules for each copper sulfate formula unit. These water molecules are called water of crystallization.

10. What is the easiest way to learn 100 chemical formulas?

Learn common element symbols and polyatomic ions first. Divide the list into acids, bases, salts, gases, organic compounds and hydrates. Use flashcards, written recall and spaced revision to strengthen memory.