Atom vs Ion

An Atom is the smallest and an indivisible unit of matter. Ions are Atoms where the protons and the electrons are not equal. Ions would therefore be either positive or negatively charged.

An Atom is composed of Protons, Neutrons and electrons. The protons and neutrons form the nucleus of the Atom while electrons surround the nucleus. An Atom remains electrically neutral till the number of electrons and protons are equal. An Atom with unequal number of electrons and protons is electrically charged and called an Ion. If the number of electrons is more than protons it is called a Cation and if the protons are more than electrons it is called anion.

An Atom is the smallest particle of an element which can take part in a chemical reaction whereas the Ions are not capable of taking part in chemical reactions. Ions can, however, exist independently in a solution, whereas, Atoms may or may not be able to exist independently.

The outermost shells of Atoms may or may not satisfy the duplet or octet rule of chemistry while the Ions will have duplet or octet in their outermost shells. Atoms are unstable as they do not have electrostatic force of attraction with the exception being noble gasses. They lose or share electron to gain stability. Ions on the other hand are stable as they have the electrostatic force of attraction between them.

Atoms combine to form a molecule. The Ions on the other hand form an electrovalent bond.

Summary:
1. An Atom is the smallest and an indivisible unit of matter. Ions are Atoms with an electrical charge.
2. In an Atom the number of electrons and protons will be equal while in an ion they would be unequal.
3. An Atom can take part in a chemical reaction while an ion cannot.
4. An ion can exist independently while an Atom cannot.
5. Atoms are generally unstable while Ions are stable.
6. Atoms combine to form a molecule while Ions form an electrovalent bond.