It is true that copper and rubber, both have electrons but copper has free electrons, which are responsible for flow of current and hence, conduct electricity.

Rubber, on the other hand, does not have free electrons and cannot conduct electricity and are called insulators

Introduction:
Both copper and rubber contain electrons, but copper is a conductor of electricity while rubber is an insulator. The difference lies in the behavior of electrons within the materials. In this response, we will explore the reasons behind this distinction in detail.

Atomic Structure:
- Copper and rubber, like all other materials, are made up of atoms.
- Atoms consist of a central nucleus composed of protons and neutrons, surrounded by orbiting electrons.
- Electrons are negatively charged particles that play a crucial role in electric conduction.

Conduction in Copper:
- Copper is a metal and an excellent conductor of electricity.
- In copper, the valence electrons (electrons in the outermost shell) are loosely bound to the atoms.
- These valence electrons are free to move within the structure of the metal.
- When an electric field is applied, these "free electrons" are easily able to move from one atom to another, carrying electric charge along the way.
- This movement of electrons is what allows copper to conduct electricity.

Insulation in Rubber:
- Rubber, on the other hand, is an insulator or a non-conductor of electricity.
- In rubber, the valence electrons are tightly bound to the atoms.
- These electrons are not free to move and are effectively localized around their respective atoms.
- As a result, rubber cannot support the movement of electrons and does not allow the flow of electric charge.
- The tightly bound electrons in rubber make it an insulator.

Band Theory:
- The behavior of electrons in conductive and insulating materials can be explained by the concept of energy bands in solid-state physics.
- In conductors like copper, there is a partially filled band called the "conduction band" that allows electrons to move freely.
- In insulators like rubber, there is a large energy gap between the valence band (occupied by electrons) and the conduction band.
- This energy gap prevents the easy movement of electrons, making rubber an insulator.

Conclusion:
In summary, the difference between the conduction of electricity in copper and rubber lies in the behavior of electrons within the materials. Copper, being a metal, has loosely bound valence electrons that are free to move and carry electric charge, making it a good conductor. On the other hand, rubber, being an insulator, has tightly bound valence electrons that cannot move freely, preventing the flow of electric charge. Understanding the atomic structure and the behavior of electrons helps explain why copper conducts electricity while rubber does not.