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Anions and Cations

In an ion, the number of electrons is different to the number of protons.

This imbalance causes ions to be charged. If there are more protons than electrons, then the ion is positively charged. If there are more electrons than protons, then the ion is negatively charged.

Positively charged ions are called cations

A positively charged ion is called a cation.

The relative charge of a cation depends on how many more protons there are than electrons. For example, if an ion has 26 protons and 23 electrons, then it will have a relative charge of +3 due to the fact that there are three more protons than electrons.

Negatively charged ions are called anions

A negatively charged ion is called an anion.

The relative charge of an anion depends on how many more electrons it has than protons. For example, if an ion has 8 protons and 10 electrons then it will have a relative charge of -2, due to the fact that it has two more electrons than protons.

Cations and anions are named differently

The naming of cations is very simple. Each cation's name is simply the name of its element followed by the word 'ion'.

For example, if an ion of the element sodium is positively charged, then it is simply called a 'sodium ion'.

The naming of anions is slightly more complicated. When naming an anion, the end of the element's name is taken off and replaced with '-ide'.

For example, a negatively charged ion of oxygen is called an oxide ion and a negatively charged ion of hydrogen is called a hydride ion.

The names of common anions that you will come across are shown below. You should learn them.

ElementName of Anion
HydrogenHydride ion
OxygenOxide ion
SulfurSulfide ion
FluorineFluoride ion
ChlorineChloride ion
BromineBromide ion
IodineIodide ion


Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.


What are positively charged ions called?


What are negatively charged ions called?


How do you work out the relative charge of an ion?


How are cations named?


How are anions named?


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