Atomic structure

• Atom


  Smallest unit of an element that retains its chemical properties
• Nucleus


  Central core of an atom containing protons (+) and neutrons (neutral)
• Electrons


  Negatively charged particles orbiting the nucleus in shells
• Protons


  Positively charged particles in the nucleus
• Neutrons


  Neutral particles in the nucleus
• Atomic Number (Z)


  Number of protons in an atom
• Mass Number (A)


  Sum of protons and neutrons in the nucleus
• Electron Shells


  • Energy levels around the nucleus where electrons are found
  • 1st shell: Can hold up to 2 electrons
  • 2nd shell: Can hold up to 8 electrons
  • 3rd shell: Can hold up to 18 electrons
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Isotopes


  • Carbon-12 (12C)
  • Carbon-14 (14C)
• Electron Distribution


  Arrangement of electrons in an atom's electron shells
• Protons determine the element's identity (atomic number)
• Neutrons and protons together determine the mass number
• Electrons occupy shells around the nucleus