01. The system of units: A set of fundamental and derived units is called system of units.
2. Ampere: One ampere is the unit of current equal to a flow of one coulomb per second.
3. Mole: The gram atomic mass or gram molecular mass or gram formula mass of any substance is called mole.
Which contains 6.02 * 10^23 particles.
4. Atom: The smallest particle of a chemical element that can exist.
5. Coulomb: The SI unit of electric charge equal to the quantity of electricity conveyed in one second by a current of one ampere.
