Each atom is made up of an inner core called the nucleus.  – Most of the atom’s mass is located in the relatively small nucleus.  – The rest of the atom is comprised of a relatively large region outside the nucleus where the electrons are found. – The atom is made of 3 subatomic particles:

Dalton’s Model of the atom. It is the basis of our understanding of the nature of matter. The following four statements comprise Dalton’s Model: a –  All matter is made up of extremely tiny. particles. called atoms. b-  Atoms are indivisible. c – Atoms of the same element are alike. d –  Atoms of different

The law of Conservation of Mass states that the mass of matter before and after a chemical change remains the same. The number of atoms also remains the same. The only thing that changes is the arrangement of the atoms. For example, the mass of hydrogen and oxygen before they combine to make water is