Atomic Structure and Radioactivity

• Atom


  Basic structure of atoms
• Atoms are very small, with a radius around 1 * 10 ^ of - 10 m
• Nucleus


  Central region of an atom, with a radius less than 1,000th the radius of the atom
• Nucleus


  • Contains protons (positive charge) and neutrons (no charge)
  • Has an overall positive charge
• Electrons


  Surround the nucleus and have a negative charge
• Energy levels


  Distances from the nucleus where electrons are found
• Energy levels further from the nucleus


  Are at a higher energy
• Electron arrangement changes


  1. Absorb electromagnetic radiation (e.g. light)

  2. Electron moves to higher energy level

  3. Emit electromagnetic radiation

  4. Electron returns to lower energy level
• Atomic number

  The number of protons in an atom
• Mass number


  The total number of protons and neutrons in an atom
• Calculating the number of neutrons


  Subtract the atomic number from the mass number
• Isotope


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

  An atom that has lost or gained one or more electrons, giving it an overall positive or negative charge
• When an atom loses one electron


  The ion has a +1 charge
• When an atom loses two electrons


  The ion has a +2 charge
• Atoms can also gain electrons to form negative ions
• The number of electrons in an atom is equal to the number of protons
• Atoms have no overall charge because the positive charge of the protons is cancelled out by the negative charge of the electrons