Particles that keep their own seperate identities like rain drops are considered to be what?

Particles that keep their own separate identities like rain drops are considered to be mixtures.

Explanation:

When two or more different compositions are mixed together, they can be form mixture and compound. The difference between mixture and compound is that in mixture each particle will be having their own separate identities. While in compound the particles will get diffused in each other forming a completely new material with new identities. Thus, if particles keep their own separate identities like rain drops, then those particles are said to form mixtures and not compounds.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.