atomic structure and the periodic table

• Atoms


  The basic units of all matter
• Atoms

  • Made up of protons, neutrons and electrons
  • Protons and neutrons in the nucleus, electrons orbit the nucleus
• Subatomic particles


  • Protons
  • Neutrons
  • Electrons
• Proton


  Positively charged particle in the nucleus
• Neutron


  Neutral particle in the nucleus
• Electron


  Negatively charged particle orbiting the nucleus
• Atomic number


  Number of protons in the nucleus
• Mass number


  Sum of protons and neutrons in the nucleus
• Atoms have no overall electrical charge as the number of protons equals the number of electrons
• Electronic structure


  1. Electrons orbit the nucleus in fixed electron shells

  2. Shells closer to nucleus have lower energy electrons

  3. Shells can only hold a maximum number of electrons
• Atoms with incomplete outer electron shells are unstable and will react to gain a complete outer shell