ATOMIC NATURE OF MATTERDOE-HDBK-1019/1-93Atomic and Nuclear PhysicsAtomic Nature of Matter SummaryAtoms consist of three basic subatomic particles. These particles are the proton, theneutron, and the electron.Protons are particles that have a positive charge, have about the same mass as ahydrogen atom, and exist in the nucleus of an atom.Neutrons are particles that have no electrical charge, have about the same mass as ahydrogen atom, and exist in the nucleus of an atom.Electrons are particles that have a negative charge, have a mass about eighteenhundred times smaller than the mass of a hydrogen atom, and exist in orbital shellsaround the nucleus of an atom.The Bohr model of the atom consists of a dense nucleus of protons and neutrons(nucleons) surrounded by electrons traveling in discrete orbits at fixed distancesfrom the nucleus.Nuclides are atoms that contain a particular number of protons and neutrons.Isotopes are nuclides that have the same atomic number and are therefore the sameelement, but differ in the number of neutrons.The atomic number of an atom is the number of protons in the nucleus.The mass number of an atom is the total number of nucleons (protons and neutrons) inthe nucleus.The notation AZX is used to identify a specific nuclide. "Z" represents the atomicnumber, which is equal to the number of protons. "A" represents the massnumber, which is equal to the number of nucleons. "X" represents the chemicalsymbol of the element.Number of protons = ZNumber of electrons = ZNumber of neutrons = A - ZThe stability of a nucleus is determined by the different forces interacting withinit. The electrostatic force is a relatively long-range, strong, repulsive force thatacts between the positively charged protons. The nuclear force is a relativelyshort-range attractive force between all nucleons. The gravitational force thelong range, relatively weak attraction between masses, is negligible compared tothe other forces.NP-01Page 10Rev. 0
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business