The difference between ion and atom are given in the table below. But before that one needs to be clear of what is an atom and ion.
Atom is the basic unit of matter. A group of atoms makes up matter. These atoms have a nucleus, with protons and neutrons in it. This nucleus is surrounded by electrons revolving in orbits. The atoms are stable entities and a matter cannot be broken further as atoms are the last states of matter.
However, atoms can form bonds with similar atoms or different atoms to form elements and compounds respectively.
Examples: Two atoms of Hydrogen form hydrogen gas H2 which is an element. Sodium is another atom which forms a metal.
Whereas an atom of Sodium and Chlorine form a compound called as hydrochloric acid (HCl). While an atom of Sodium and chlorine form sodium chloride.
Ion: Ions are atoms which are devoid of few electrons or have few additional electrons.
Example: Hydrogen is an atom and is represented as H while it can form ion and is represented as H+. The ‘+’ indicated the loss of one electron in the hydrogen atom.
The ions are formed only when they are broken from a molecule by use of some forces of attraction or high energy in the form of heat or radiation.
For example, HCl is a molecule of hydrogen and chlorine. But when this molecule is put in water, it converts in two ions as H+ and Cl-.
Both these ions exist in water and can even react with other ions. The water molecules exert forces like Vanderwal forces of attraction or hydrogen bonding to separate the ions from the molecule.
Since the chlorine is a high electronegative atom, it takes away the electron of hydrogen to have one additional electron in its outer orbit (Cl-) and hydrogen being weak gives up the electron from its outer orbit and stay without any electron as H+.
However, an atom would exist as an atom in any solvent and is most stable. The best examples for atom form of matter is noble gases like helium, neon, argon, krypton. These have a single and stable atom (monoatomic) which retain their form in different conditions.
| Features | Atom | Ion |
| Existence | Single atoms exist naturally as noble gases | Ions exists only under external influences of temperature, inter molecular forces etc. |
| Stability | Atoms are more stable and some of them form bons with similar atoms to form a stable molecule. | Ions are least stable and have a tendency to attain ground state i.e. again back to atom state or merge to form molecule. |
| Charge | The net electric charge on atoms can be zero | The net electric charge on ions is either positive or negative charge. |
| Conduction movement | Atoms are electrically neutral so, they do not move under the influence of electricity. | Ions are charged so when exposed to electric current, they move towards the oppositely charged electrodes. |
| Bonds | Atoms mostly have covalent bonds. | Ions tend to have ionic bonds. |
| Chemical reactions | Atoms are less reactive. | Ions are highly reactive. Hence, the acids like sulfuric acid, bases like sodium hydroxide are strong because of the ions in them. When exposed, they react instantly |