Chemical Symbols: All 118 Elements, Names, Symbols & Atomic Numbers

Chemical symbols arae the standardized short forms used to represent chemical elements. They are found throughout chemistry textbooks, laboratory work, chemical formulas, equations, scientific research, and the periodic table. For example, H represents hydrogen, O represents oxygen, Na represents sodium, and Fe represents iron.

At first, chemical symbols may look like simple abbreviations, but there is an important difference: a chemical symbol is part of an internationally standardized system of chemical notation. Every officially recognized element has its own symbol, and the capitalization of that symbol matters.

Some symbols are easy to remember because they closely match the English element name. Others seem unrelated until you learn their historical or Latin origins. Na for sodium, Fe for iron, Ag for silver, Au for gold, and W for tungsten are common examples.

This guide provides a complete reference to the 118 chemical elements and their symbols, explains how symbols are written, shows why some symbols do not match modern English names, and explains how chemical symbols are used in formulas, ions, and chemical equations.

What Are Chemical Symbols?

A chemical symbol is a one- or two-letter notation used to identify a chemical element.

For example:

• H = hydrogen
• C = carbon
• N = nitrogen
• O = oxygen
• Na = sodium
• Cl = chlorine
• Fe = iron
• Au = gold

The symbol identifies the element, while additional numbers or signs can provide more information about atoms, molecules, ions, or quantities.

There are currently 118 officially named chemical elements in the periodic table. IUPAC, the International Union of Pure and Applied Chemistry, maintains the internationally recognized names and symbols of the elements. The four most recently named elements—nihonium, moscovium, tennessine, and oganesson—received their official names and symbols in 2016.

A chemical symbol is therefore much more than an ordinary abbreviation. It is a standardized way of communicating about an element regardless of the language used by the scientist or student.

Complete List of All 118 Chemical Symbols

The table below provides a complete chemical symbols list arranged by atomic number.

The names and symbols in the table follow the internationally standardized element system represented by IUPAC. IUPAC’s periodic-table resources list the symbols and names for elements through atomic number 118.

How Chemical Symbols Are Written

Chemical symbols follow specific capitalization rules. These rules are important because changing a capital letter to lowercase—or vice versa—can change whether the notation represents a recognized element symbol.

One-Letter Chemical Symbols

If an element has a one-letter symbol, that letter is always uppercase.

Examples include:

• H — Hydrogen
• B — Boron
• C — Carbon
• N — Nitrogen
• O — Oxygen
• F — Fluorine
• P — Phosphorus
• S — Sulfur
• K — Potassium
• V — Vanadium
• Y — Yttrium
• I — Iodine
• W — Tungsten
• U — Uranium

There are only a limited number of one-letter element symbols, so these are worth learning separately.

Two-Letter Chemical Symbols

Most element symbols contain two letters.

The first letter is uppercase, while the second letter is lowercase.

Examples:

• He — Helium
• Li — Lithium
• Na — Sodium
• Mg — Magnesium
• Al — Aluminum
• Si — Silicon
• Cl — Chlorine
• Ca — Calcium
• Fe — Iron
• Cu — Copper
• Ag — Silver
• Au — Gold

The capitalization is part of the notation. Therefore, Cl is the chemical symbol for chlorine, not CL.

Why Capitalization Matters

Consider these examples:

A common student mistake is to capitalize both letters because the symbol looks like an abbreviation. In chemistry, that is not the standard format.

Why Some Chemical Symbols Do Not Match the Element Name

One of the most interesting parts of learning chemical symbols and meanings is discovering that some symbols are based on historical or Latin names rather than modern English names.

For example, there is no obvious reason for English-speaking students to expect sodium to be Na or iron to be Fe.

The explanation comes from the history of chemical naming.

Sodium — Na

The symbol for sodium is Na.

It is associated with the historical name natrium, which explains why the symbol does not begin with S.

Potassium — K

Potassium uses the symbol K, which comes from kalium.

This is why potassium does not use a symbol such as “Po” or “P.” The letter P is already associated with phosphorus.

Iron — Fe

Iron is represented by Fe, from the Latin ferrum.

This is one of the most important unusual symbols for students to memorize.

Copper — Cu

Copper uses Cu, derived from cuprum, the Latin name associated with copper.

Silver — Ag

Silver is represented by Ag, from the Latin argentum.

Tin — Sn

Tin uses Sn, from the Latin stannum.

Antimony — Sb

Antimony has the symbol Sb, associated with the Latin stibium.

Gold — Au

Gold is represented by Au, from the Latin aurum.

Mercury — Hg

Mercury uses Hg, derived from the historical name hydrargyrum.

Lead — Pb

Lead is represented by Pb, from the Latin plumbum.

Tungsten — W

Tungsten has perhaps one of the most surprising symbols: W.

The symbol comes from the historical name wolfram, rather than the modern English word tungsten.

The Most Important Historical Symbols to Memorize

These unusual symbols are much easier to remember when you learn where they came from rather than trying to memorize them as random letters.

Chemical Symbols on the Periodic Table

The periodic table organizes elements according to their atomic number and recurring chemical properties.

A typical element box contains information such as the element’s atomic number, symbol, name, and atomic-weight information.

For example, a simplified carbon entry might look like:

6 — C — Carbon

Here:

• 6 = atomic number
• C = chemical symbol
• Carbon = element name

The atomic number identifies the number of protons in the nucleus of an atom of that element.

IUPAC’s official periodic-table materials provide standardized element names, symbols, and atomic-number information and also explain the conventions used for atomic-weight data.

Atomic Number vs. Chemical Symbol

These two pieces of information should not be confused.

Atomic number is a number.

Chemical symbol is a letter-based identifier.

For example:

8 O Oxygen

• 8 = atomic number
• O = symbol
• Oxygen = name

The atomic number is unique to the element, while the chemical symbol is its standardized letter representation.

Chemical Symbols vs. Chemical Formulas

A chemical symbol represents an element, while a chemical formula represents a substance and combines one or more element symbols.

For example:

• H = hydrogen
• O = oxygen
• H₂O = water

The formula H₂O contains the chemical symbols H and O.

Other examples include:

A formula therefore gives more information than a single element symbol.

How Subscripts and Coefficients Work

Numbers in chemical notation can be confusing for beginners, especially when a formula contains both subscripts and coefficients.

Consider:

2H₂O

There are two different numbers here.

The 2 before H₂O is a coefficient.

The 2 after H is a subscript.

What Does a Subscript Mean?

In H₂O, the subscript 2 tells us that each water molecule contains two hydrogen atoms.

Therefore:

H₂O = 2 hydrogen atoms + 1 oxygen atom

What Does a Coefficient Mean?

In 2H₂O, the coefficient 2 tells us that there are two water molecules.

Therefore:

2H₂O = 4 hydrogen atoms + 2 oxygen atoms

This distinction becomes particularly important when balancing chemical equations.

Chemical Symbols vs. Ions

A chemical symbol can also appear with a charge when representing an ion.

For example:

• Na = sodium as an element
• Na⁺ = sodium ion
• Cl = chlorine as an element
• Cl⁻ = chloride ion
• Mg²⁺ = magnesium ion
• Ca²⁺ = calcium ion
• Fe²⁺ = iron(II) ion
• Fe³⁺ = iron(III) ion

The chemical symbol identifies the element, while the superscript charge indicates that the particle is an ion with an electrical charge.

This is why Fe, Fe²⁺, and Fe³⁺ should not automatically be treated as identical notation.

Chemical Symbols in Chemical Equations

Chemical symbols are essential building blocks of chemical equations.

For example:

2H₂ + O₂ → 2H₂O

This equation represents hydrogen reacting with oxygen to form water.

The individual symbols are:

• H = hydrogen
• O = oxygen

The subscripts and coefficients provide additional quantitative information.

Chemical equations use this compact notation because writing every element name in full would make chemical reactions much harder to read and balance.

Common Chemical Symbols Students Should Learn First

Although there are 118 elements, beginners do not need to memorize all of them at once.

A practical starting group includes elements that frequently appear in introductory chemistry, formulas, laboratory examples, and science classes.

Start with the symbols that closely resemble their element names. After that, concentrate on the symbols derived from historical names.

Most Commonly Confused Chemical Symbols

Some element symbols are particularly easy to confuse because they use similar letters.

C, Ca, and Cl

These three symbols are different:

• C = Carbon
• Ca = Calcium
• Cl = Chlorine

The lowercase second letter matters.

N and Na

• N = Nitrogen
• Na = Sodium

P and Pb

• P = Phosphorus
• Pb = Lead

S and Si

• S = Sulfur
• Si = Silicon

Co and C

• Co = Cobalt
• C = Carbon

Al and Ag

• Al = Aluminum
• Ag = Silver

Ca and Cd

• Ca = Calcium
• Cd = Cadmium

Learning the complete symbol rather than only its first letter prevents many common mistakes.

Chemical Symbols by Element Category

Chemical symbols become easier to understand when the elements are considered within the broader structure of the periodic table.

Alkali Metal Symbols

The alkali metals in Group 1, excluding hydrogen from the usual alkali-metal category, include:

Li, Na, K, Rb, Cs, Fr

These represent:

• Lithium
• Sodium
• Potassium
• Rubidium
• Cesium
• Francium

Hydrogen occupies Group 1 but has properties that distinguish it from the alkali metals.

Alkaline Earth Metal Symbols

The Group 2 elements are:

Be, Mg, Ca, Sr, Ba, Ra

They represent:

• Beryllium
• Magnesium
• Calcium
• Strontium
• Barium
• Radium

Halogen Symbols

The halogens are:

F, Cl, Br, I, At, Ts

They represent:

• Fluorine
• Chlorine
• Bromine
• Iodine
• Astatine
• Tennessine

Noble Gas Symbols

The noble gases are:

He, Ne, Ar, Kr, Xe, Rn, Og

They represent:

• Helium
• Neon
• Argon
• Krypton
• Xenon
• Radon
• Oganesson

Lanthanide Symbols

The lanthanides are commonly represented by:

La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu

These elements are often displayed in a separate row beneath the main body of the periodic table.

Actinide Symbols

The actinides are:

Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr

These are also commonly shown in a separate row below the main periodic-table body.

Why Element Symbols Are International

Element names can differ between languages, but chemical symbols provide a common scientific notation system.

For example, the symbol Fe identifies iron in scientific communication regardless of whether the surrounding explanation is written in English, Spanish, French, German, Urdu, or another language.

This international character is one reason chemical symbols are so useful in science education and research.

The standardized names and symbols are maintained through international chemical nomenclature and periodic-table work associated with IUPAC.

How Chemical Symbols Were Standardized

Modern chemical symbols developed from earlier systems of chemical notation. The letter-based system associated with element names became a practical way to communicate chemical information internationally.

Historical names also remained embedded in the symbols of several elements. This explains why modern English names do not always predict their symbols.

The periodic table itself has also developed over time. The completion of the seventh period followed the verification and naming of elements 113, 115, 117, and 118. IUPAC formally approved the names and symbols Nh, Mc, Ts, and Og in November 2016.

This history explains why older chemistry resources may contain temporary names or symbols for elements that now have official names.

The Four Most Recently Named Elements

The four elements that completed the seventh period received their official names and symbols in 2016:

IUPAC approved these names and symbols after a public-review process.

This is useful to know because older periodic tables may show temporary systematic names instead.

How to Memorize Chemical Symbols

Trying to memorize all 118 symbols in one sitting is usually inefficient. A better method is to organize them into groups.

Start With Symbols That Match the Element Name

Learn easy examples first:

H, C, N, O, F, B, S, P

Then move to two-letter symbols:

He, Li, Be, Ne, Mg, Al, Si, Cl, Ca

Once these become familiar, the longer list becomes less intimidating.

Learn Historical Symbols as a Separate Group

A useful memory group is:

Na, K, Fe, Cu, Ag, Sn, Sb, W, Au, Hg, Pb

These are easier to remember when associated with their historical names.

For example:

Fe → ferrum → iron

Au → aurum → gold

Ag → argentum → silver

Pb → plumbum → lead

Learn Symbols Through Chemical Formulas

Instead of memorizing symbols in isolation, connect them to formulas you already know.

For example:

H₂O

contains H and O.

CO₂

contains C and O.

NaCl

contains Na and Cl.

CaCO₃

contains Ca, C, and O.

This approach gives each symbol a practical context.

Use Short Daily Practice Sessions

Rather than trying to memorize the complete periodic table immediately, practice a small group of symbols at a time.

For example:

Day 1: H, C, N, O, F

Day 2: Na, Mg, Al, Si, P

Day 3: S, Cl, K, Ca, Fe

Day 4: Co, Ni, Cu, Zn, Ag

Then review all previously learned symbols before adding another group.

Chemical Symbols Practice Quiz

Test yourself before checking the answers.

1. What element does Fe represent?
2. What element does Au represent?
3. What element does Na represent?
4. What element does K represent?
5. What element does Ag represent?
6. What element does Pb represent?
7. What element does Cu represent?
8. What element does Hg represent?
9. What element does Cl represent?
10. What element does W represent?

Answers

1. Fe = Iron
2. Au = Gold
3. Na = Sodium
4. K = Potassium
5. Ag = Silver
6. Pb = Lead
7. Cu = Copper
8. Hg = Mercury
9. Cl = Chlorine
10. W = Tungsten

If you can identify these quickly, you have already learned several of the most important unusual chemical symbols.

Common Mistakes When Writing Chemical Symbols

Capitalizing Both Letters

Writing CL instead of Cl is incorrect standard chemical notation.

The correct symbol is:

Cl

Using Only the First Letter

Sodium is not represented by S.

Its symbol is:

Na

The symbol S represents sulfur.

Confusing Element Symbols With Formulas

O and O₂ are not the same notation.

O is the symbol for oxygen.

O₂ represents a molecule containing two oxygen atoms.

Confusing Coefficient and Subscript

In 2H₂O, the first 2 and the second 2 have different meanings.

• First 2 = coefficient
• Second 2 = subscript

Assuming Every Symbol Comes From the English Name

This is particularly problematic with:

Na, K, Fe, Cu, Ag, Sn, Sb, W, Au, Hg, Pb

Many of these symbols have historical or Latin origins.

Why Chemical Symbols Matter in Everyday Chemistry

Chemical symbols are not limited to school chemistry.

They are used to describe materials, medicines, minerals, laboratory substances, industrial processes, environmental measurements, and many other scientific subjects.

You may encounter them when reading about:

• iron (Fe)
• calcium (Ca)
• sodium (Na)
• potassium (K)
• oxygen (O)
• carbon (C)
• hydrogen (H)
• chlorine (Cl)
• zinc (Zn)
• copper (Cu)

Once you understand the symbols, chemical formulas become much easier to interpret.

Frequently Asked Questions About Chemical Symbols

What are chemical symbols?

Chemical symbols are standardized one- or two-letter representations of chemical elements. For example, H represents hydrogen, O represents oxygen, and Fe represents iron.

How many chemical symbols are there?

There are 118 officially named chemical elements, and each has its own chemical symbol. IUPAC’s official periodic-table resources list the elements through atomic number 118.

What is the chemical symbol for hydrogen?

The chemical symbol for hydrogen is H.

What is the chemical symbol for oxygen?

The chemical symbol for oxygen is O.

What is the chemical symbol for carbon?

The chemical symbol for carbon is C.

What is the chemical symbol for nitrogen?

The chemical symbol for nitrogen is N.

What is the chemical symbol for sodium?

The chemical symbol for sodium is Na. The symbol is associated with the historical name natrium.

Why is the symbol for potassium K?

Potassium uses K, which comes from the historical name kalium.

Why is iron represented by Fe?

Iron is represented by Fe, derived from the Latin ferrum.

Why is gold represented by Au?

Gold uses Au, from the Latin aurum.

Why is silver represented by Ag?

Silver uses Ag, from the Latin argentum.

Why is tungsten represented by W?

Tungsten uses W, associated with its historical name wolfram.

Why is lead represented by Pb?

Lead uses Pb, derived from the Latin plumbum.

What is the difference between a chemical symbol and a chemical formula?

A chemical symbol identifies an individual element, such as O for oxygen. A chemical formula combines element symbols to represent a substance, such as H₂O for water.

What is the difference between a chemical symbol and an ion?

A chemical symbol identifies an element, while an ion is represented by an element symbol with a charge when the particle has an electrical imbalance. For example, Na represents sodium, while Na⁺ represents a sodium ion.

Are chemical symbols always capitalized?

The first letter of every chemical symbol is uppercase. If a symbol has a second letter, that letter is lowercase. Examples include H, O, Na, Fe, and Cl.

Can a chemical symbol have three letters?

Official element symbols are one or two letters. Some temporary systematic names used during the naming process have historically involved three-letter temporary symbols, but the officially named elements use one- or two-letter symbols. IUPAC’s current periodic table lists the official symbols through element 118.

What are the easiest chemical symbols to memorize?

Symbols such as H, C, N, O, F, P, S, K, I, U are one-letter symbols and can be learned separately. Two-letter symbols that closely resemble the element name, such as He, Li, Mg, Ca, Cl, and Ne, are also relatively straightforward.

Which chemical symbols are hardest to remember?

Students often find Na, K, Fe, Cu, Ag, Sn, Sb, W, Au, Hg, and Pb difficult because they are based on historical or Latin names rather than simply taking the first letters of the English element name.

What does the number after a chemical symbol mean?

A number written as a subscript usually tells you how many atoms of that element occur in a chemical formula. For example, the 2 in H₂O means that the formula contains two hydrogen atoms for each oxygen atom.

What does a number before a chemical formula mean?

A number placed before a formula is called a coefficient. In 2H₂O, the coefficient 2 indicates two water molecules or two formula units, depending on the substance being represented.

Are chemical symbols the same in different languages?

Chemical symbols are designed as internationally standardized scientific notation, so the symbol generally remains the same even when the element’s name changes between languages.

Quick Chemical Symbols Reference

For fast revision, these are some of the most useful symbols to remember:

H — Hydrogen
He — Helium
C — Carbon
N — Nitrogen
O — Oxygen
F — Fluorine
Na — Sodium
Mg — Magnesium
Al — Aluminum
Si — Silicon
P — Phosphorus
S — Sulfur
Cl — Chlorine
K — Potassium
Ca — Calcium
Fe — Iron
Co — Cobalt
Ni — Nickel
Cu — Copper
Zn — Zinc
Ag — Silver
I — Iodine
Au — Gold
Hg — Mercury
Pb — Lead
U — Uranium

For the complete reference, use the 118-element table above.

Final Takeaway

Chemical symbols are the universal shorthand of chemistry. They allow scientists and students to identify elements quickly and use those elements in formulas, equations, molecular descriptions, and scientific communication.

The most important rules are simple:

• Every officially recognized element has its own chemical symbol.
• A one-letter symbol is uppercase.
• A two-letter symbol begins with an uppercase letter and ends with a lowercase letter.
• Chemical symbols are different from complete chemical formulas.
• Subscripts and coefficients provide additional information in formulas and equations.
• Some symbols come from historical or Latin names rather than modern English names.
• There are currently 118 officially named elements.
• IUPAC provides the internationally standardized names and symbols used in the periodic table.

If you are beginning chemistry, start by learning the common symbols and then focus on the unusual ones such as Na, K, Fe, Cu, Ag, Au, Hg, Pb, and W. Once these become familiar, reading the periodic table and understanding chemical formulas becomes considerably easier.

Sources for Chemical Element Names and Symbols

For authoritative verification of element names, symbols, atomic numbers, and periodic-table information, consult the International Union of Pure and Applied Chemistry (IUPAC). Its current periodic-table resources provide the standardized element information, while its 2016 announcement documents the formal approval of the names and symbols for elements 113, 115, 117, and 118.

Henry Sullivan

I’m Henry Sullivan, a writer interested in English vocabulary, modern expressions, and changing language trends. I enjoy looking beyond a basic dictionary definition to understand how people actually use words. At Meanera, I share clear explanations and examples that make unfamiliar words and phrases easier to understand.

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