Define mole.

Hint: We know that the SI units or International System of Units is a modern form of metric system. This system of measurement is official in all countries. In this system seven units present, they are, metre (unit of length), Second (unit of time), ampere (unit of current),kilogram (unit of mass ),mol (unit of amount of substance), kelvin (unit of temperature) and candela (unit of luminous density).

Complete step by step answer: Mole is a Latin word whose meaning is pile or mass of stones placed in sea. The mole or mol (abbreviation form) is the SI unit which measures the amount of substance present. A mole is the term that defines the number of carbon (C) atoms in 12 g of pure carbon. After so many years of experiment, it has been proved that a mole of anything contains $6.022 \times {10^{23}}$ representative particles.

Additional Information: The number $6.022 \times {10^{23}}$ is named in honor of the Italian physicist Amedeo Avogadro. The Avogadro's number aids in counting very small particles. Different kinds of particles, such as molecules, atoms, ions, electrons are representative particles. One mole of anything consists of $6.022 \times {10^{23}}$ representative particles. For example, one mole of oxygen consists of $6.022 \times {10^{23}}$ molecules of oxygen. Hence, the relation between mole and Avogadro’s number is \[1\;{\rm{mol}} = 6.022 \times {10^{23}}\;{\rm{particles}}\]

Note: There is a close analogy between ‘dozen’ and ‘mole’. A dozen always represent twelve articles. They may be apples, organs etc. In a similar manner a moles represents $6.022 \times {10^{23}}$ particles which may be of atoms, molecules, ions, electrons, protons, neutrons etc. Therefore, a mole is often called a chemist's dozen.