When objects exchange charge, why do we say it's the negative charge that moves and not the positive?

It is said that the negative charge moves because the electrons in the atoms of any object are taken or given to the atoms of another object.

Explanation:

The atom is made up of protons, electrons and neutrons. The number of protons is exactly the same to the number of electrons for a certain element. For example, hydrogen: it has a proton, and therefore, an electron.

The electron has a negative charge. The proton has a positive charge. And the neutron has no charge, so it is neutral. While the atom has the same number of protons and electrons, it will not be electrically charged.

An example of how a charge exchange occurs between two objects is through the case of rubbing. This makes the atoms of the two objects close enough that there is an electron transfer, causing any of the objects to gain or lose electrons as a consequence of each other interaction. In the case of transferring electrons, the atom will have a greater number of protons, so it will be positively charged. When the atom receive electrons, it will have a greater number of electrons, so it will be negatively charged.

Therefore, since it is the electrons that move from one atom to another, then it is the negative charge that moves (characterized by the electrons) and not the positive charge (characterized by the protons).