Chapter+2.4


 * Atoms Consist of Protons, Neutrons, and Electrons** 2.4

Atoms are the smallest unit of matter that still retain properties of an element. Within an atom, there are protons, neutrons, and electrons. Protons and neutrons are found in the nucleus of the atom. Protons have a single positive electrical charge (+), and neutrons have no charge. Electrons have a single negative electrical charge (-)**.**


 * Mass Number (atomic mass**): The sum of the numbers of protons and neutrons in its nucleus.


 * Isotope****:** Elements with variant forms. The element has the same amount of protons and electrons, but different amount of neutrons.


 * Radioactive isotope:** When an isotope's nucleus decays spontaneously, giving off particles of energy.

IONS: Ions are atoms that have gained or lost electrons, and therefore are charged.