What is a chemical symbol?

A chemical symbol is a shorthand way of representing an element, usually consisting of one or two letters from its name.

How should a two-letter chemical symbol be written?

The first letter is always a capital letter, and the second letter is always lowercase.

What does a chemical formula tell us?

A chemical formula shows the symbols of the elements in a compound and the ratio of atoms for each element.

What is the symbol for the element Sodium?

The chemical symbol for Sodium is Na.

How do you name a compound containing a metal and a non-metal?

The metal comes first, followed by the non-metal, which usually has its ending changed to '-ide'.

Symbols and formulae

Elements and symbols

Elements

An element is a substance that is made of only one kind of atom, and cannot be split into simpler substances. Some examples of elements are oxygen, hydrogen, gold, and iron.

Symbols Elements are shown by letters from the alphabet. These letters are also called symbols. The symbol for an element is either a single capital letter or a capital letter with a lower case letter after it.

For example:

H = Hydrogen
He = Helium
Li = Lithium
Be = Beryllium
N = Nitrogen
O = Oxygen
F = Fluorine

The periodic table

There are 118 chemical elements listed in the periodic table:

Periodic table of elements.

94 chemical elements occur naturally on Earth and in the universe.
24 elements are made using nuclear reactions.

Compounds and molecules

Compounds

A compound is a substance that has atoms of two or more different elements.

The atoms of the elements are joined together by chemical bonds in a fixed ratio of atoms.

The formula of a compound shows how many atoms of each element are in the compound.

The formula is made of symbols and numbers.

The numbers are written as subscript, which means they are smaller and lower than the symbol. For example, the formula for water is H2O.

For example:

Water is a compound of hydrogen and oxygen. It has the symbol H for hydrogen and the symbol O for oxygen. The formula for water is H2O.
Oxygen gas is a molecule of two oxygen (O) atoms. It has the symbol O for oxygen. The formula for oxygen gas is O2.

H2O = Two atoms of hydrogen, one atom of oxygen = 3 atoms in total
CO2 = One atom of carbon, two atoms of oxygen = 3 atoms in total

Molecules

Most molecules are made of two or more non-metal atoms bonded together. For example:

Water molecule.

Water molecule

Summary:

Chemical elements are shown by letters from the alphabet.
An element’s chemical symbol is either a single capital letter or a capital letter with a lower-case letter after it.
The periodic table is a chart that shows the chemical symbols for all the different elements.

Symbols and formulae

🧪 Knowledge Check: Symbols and Formulae