Difference Between Atom And Ion

atom is the smallest unit of ordinary matter or single particle that is neutral and forms a chemical element. solid, liquid, gas, and plasma are composed of ionized or neutral atoms. on the other hand, an ion is a negatively or positively charged particle. the basic difference between atom and ion is that an atom is electrically neutral or ionized and it consists of the same number of electrons and protons while an ion is an electrically charged particle. an ion consists of an unequal number of electrons and protons. it may contain one or more atoms.

Difference Between Atom And Ion in tabular Form

Atom Ion
Atoms are electrically neutral which means they have the same number of protons and electrons. ions are charged particles, positive ions (cations) or negative ions (anions).
The combination of atoms results in the formation of molecules. The combination of ions results in the formation of compounds.
These are the smallest units of elements. they are the Single-particle or collection of particles
The Independent existence of atoms is not possible. ions can exist independently.
Atoms form molecule Ions form an electrovalent bond
They have the same number of electrons and protons. they have unequal electrons and protons.
atoms are unstable. Ions are stable.
An Atom can take part in a chemical reaction. An ion cannot take part in a reaction.
atoms can form a covalent bond or ionic bond ions can form only an ionic bond

What is Atom?

the word “atom” is derived from the Greek language having means “indivisible”. the following concept was developed by an ancient Greek philosopher Democritus. he stated in his theory that actually, everything consists of atoms. while the atom is the smallest particle in the universe that cannot be sub-divided into tiny particles.

Atom is the smallest unit that matter may be divided without the release of electrically charged particles. An atom contains only one nucleus and electrons, protons revolve around this nucleus. Atom has the characteristics properties of a chemical element and is also the smallest unit of matter. Atom is the basic building block of ordinary matter. When the atoms join together they form a molecule.

this concept has developed later on by scientists and now the atom has known as a building block of matter or elements. moreover, different substances possess different kinds of atoms which are totally different in size and properties from each other. For example, hydrogen atoms are small, and gold atoms are large, atoms of neon and helium hardly interact with other atoms, and oxygen atoms do this very actively.

when atoms are further grouped together and form molecules. however, unlike Democritus, now it is possible that an atom can be sub-divided into tiny particles like electrons, protons, and neutrons.

according to scientists, there are 92 types of atoms today that exist in nature and many of them are obtained through artificial ways.

Atoms are characterized by:
  • certain very small dimensions;
  • a certain, also very small, mass;
  • a certain structure.

What is Ion?

An ion is an atom or molecule that has gained or lost one, two, or more of its valence electrons, giving it a net positive or negative electrical charge. in other words, there is an imbalance in the number of electrons and protons in the chemical species.

The word “ion” was first introduced by Micheal Faraday in 1834 to describe the chemical species that travel from one electrode to another electrode in an aqueous sloution. this word come from the Greek word ienei which means “to go”

Cations and Anions


A cation is an ion that carries a net positive charge as the number of protons in species is greater than the number of electrons. The Formula for a cation is indicated by a superscript formula that indicates the number of the charge and “+” sign. if only “+” is present, it means that the charge is “+1”. E.g. Ca2+ indicates a cation with a +2 charge.


Anion is an ion that carries a negative charge. in an anion, the number of electrons is more than the number of protons. The neutrons in an anion is not a factor in whether an atom, functional group, or molecule. Charge on an anion indicates using a superscript after a chemical formula. For E.g. Cl is a chlorine anion, which carries a single negative charge (-1).

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