Difference between cations and anions

The term ‘ion’ was 1st used by English physicist and chemist Michael Faraday in 1834 after a suggestion by English Polymath, Scientist, William Whewell.  Michael Faraday used this term for those species which were moving one electrode to another through aqueous medium. The terms ‘anion’ and ‘cation’ are also coined by Faraday and Whewell. In 1884, Swedish scientist Svante Arrhenius explained that solid crystalline salts dissociate into paired charged particles when dissolved. For this he won the Nobel prize in Chemistry in 1903. 

What is ion?

The word ion is originated from Greek word ἰόν, ion, which means ‘going’. Ions are charged species. Ion can be defined as an atom or molecule that has a net electrical charge. In an atom the number of electrons and protons is equal so they possess zero charge or neutral in nature. While in ions the number of protons are equal but number of electrons are unequal. So, they possess either positive or negative charge. Na+, O-2, NH4+, OH- etc. are examples of ions. 

Ions which are a group of elements or atoms that are covalently bonded but carry either positive or negative charge are called polyatomic ions. CN-, OH-, NH4+, NO3-, CO3-2 etc. are examples of polyatomic ions. Ions which have only one element that carry either positive or negative charge are called monoatomic ions. Na+, O-2, Al+3, Ce+3 etc. are examples of monoatomic ions. 

What is Cation? 

Those ions which possess positive charge are called cations. Na+, Al+3, Ce+3 etc. are examples of cations. When an atom loses its electron/s then it gains a positive charge due to less number of electrons than protons in its nucleus. Then this positively charged species is called cation. The term was coined by Faraday and Whewell. It is taken from the Greek word κάτω (káto) ἰόv (kation) which means ‘going down’. 

What is Anion? 

Those ions which possess negative charge are called anions. O-2 , CN-, OH- , Cl- etc. are examples of anions. When an atom gains electron/s to get stability, then it gains a negative charge due to more number of electrons than protons in its nucleus. Then this negatively charged species is called anion. The term was coined by Faraday and Whewell. It is taken from the Greek word ἄνω ἰόv (anion) which means ‘going up’.


S.No. 

Cation 

Anion 

1.

An ion or a charged particle which has a positive charge is called cation. 

An ion or a charged particle which has a negative charge is called anion. 

2.

The word cation is originated from Greek word κάτω (káto) ἰόv (kation) which means ‘going down’. 

The word anion is originated from Greek word ἄνω ἰόv (anion) which means ‘going up’.

3.

In cations the number of protons is more than the number of electrons. 

In anions the number of electrons is more than the number of protons. 

4.

Generally, metals form cations. 

Generally, non – metals form anions. 

5.

Cations get attracted towards the negatively charged electrode in electrolysis. 

Anions get attracted towards the positively charged electrode in electrolysis. 

6.

Cations are smaller in size than anions. 

Anions are generally larger in size than cations. 

7.

Cations gain electrons and convert into neutral atoms or molecules. 

Anions generally lose electrons and convert into neutral atoms or molecules. 

8.

Cations form electrostatic or ionic bonds with anions to form ionic compounds. 

Anions form electrostatic or ionic bonds with cations to form ionic compounds. 

9.

Na+, Mg+2, Ca+2, Fe+3 etc. are examples of cations. 

O-2, Cl-, Br- etc. are examples of anions.  


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