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What do the Symbols
and Numbers Mean
in Chemical Equations?
When we are balancing
we need to know what the symbols and numbers mean.
When we write an equation
for a chemical
for example Mg + Cl2 MgCl2
each atom or ion of an element
is represented by a chemical symbol.
Mg is the chemical symbol
Mg means one magnesium atom (Mg = Mg1 see below).
Cl means one chlorine atom. Cl2 means two chlorine atoms.
The formula of a compound cannot be
The formula is shown by small numbers written after
(and a little below) each element in the compound.
KCl is an
KCl means one potassium ion with one chlorine ion
(the number one is never written, KCl = K1Cl1).
Na2O means two sodium ions with one oxygen ion.
Al2O3 means two aluminium ions with three oxygen ions.
We shall look at two examples of unbalanced
You can balance any chemical equation by applying the rules
shown in these examples. Just click on an example below.
Example 1. The reaction of potassium with chlorine.
Example 2. The reaction of lithium with oxygen.
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