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Differences Between Cation and Anion

Anion

Cation

A negatively charged ion is an anion. 

Examples:  Cl-, O-2

A positively charged ion is a cation. 

Examples:  Li+, Mg+2 

A neutral atom's gain of electron(s) forms an anion (reduction reaction).

A neutral atom's loss of electron(s) forms a cation (oxidation reaction).

The size of the anion is usually larger than the parent atom. 

 

For example, Cl- has a greater ionic radius than the Cl atom.

The size of the cation is usually smaller than the parent atom. 

 

For example, Na+ has a smaller ionic radius than the Na atom.

Generally, non-metals form anions.

Metals form cations.

During electrolysis, the anion moves towards the anode, a positive electrode.

During electrolysis, the cation moves towards the cathode, a negative electrode.

Anion can also be polyatomic, where a group of atoms are held using covalent bonds, and one of the electronegative atom(s) gains the covalent bond electrons. Example: SO4-2, PO43-

Cations can also be polyatomic, where the positive charge is attained by one of the atoms in a covalently bonded molecule.

Example: NH4+, H3O+.

Heterolytic bond cleavages can form polyatomic anions. 

Post heterolytic bond cleavage, the newly formed anions form an ionic bond with an oppositely charged counterpart and exist as an ionic salt.

 

Heterolytic bond cleavages can create polyatomic cations. Post heterolytic bond cleavage, they form an ionic bond with an oppositely charged counterpart and exist as an ionic salt. 

 

 

 

 

Anions of carbon (carbanions) can also form covalent bonds.

In the case of positively charged carbocations, they form new covalent bonds.

 

 

Bonding in Atoms

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Reactive Intermediates

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