Introductory Atomic and Nuclear Physics

Objective: Relate protons, neutrons, and nuclide notation.

An atomic nucleus contains protons and neutrons; atomic number Z counts protons and determines element identity, while mass number A counts protons plus neutrons. Isotopes of an element share Z and differ in neutron count. Nuclide notation ¹⁴₆C indicates 6 protons and 8 neutrons; a neutral atom also has 6 electrons. Nuclear changes alter a nucleus and may change the element, unlike chemical changes that rearrange electrons and bonds without altering nuclear identity. Stability depends on nuclear structure and interactions, not merely whether a mass number is large. Mass number is an integer count and should not be confused with average periodic-table atomic mass.

Objective: Apply introductory atomic and nuclear physics to calculations, evidence, and specified situations.

Radioactive decay is probabilistic; a half-life gives the expected remaining undecayed fraction after a stated interval, not the exact lifetime of one nucleus. Alpha emission lowers A by four and Z by two; beta and gamma processes have other accounting rules. Nuclear fission splits a heavy nucleus, while fusion joins lighter nuclei; both require energy accounting through binding-energy differences. Electronic photons have energy E=hf. Chemical changes rearrange electrons and atoms; nuclear changes can change elemental identity. The introductory numerical exercises use mean-value decay and specified constants.