Atoms

• Atoms


  The basic building blocks of all matter
• Everything on Earth is made of atoms...even the air and your body
• Atoms


  • For some time people thought that atoms were the smallest particles and could not be broken into anything smaller
  • Scientists now know that atoms are actually made from even smaller subatomic particles
• Subatomic particles


  • Proton
  • Neutron
  • Electron
• Atoms


  Made of three particles: Protons, Neutrons, Electrons
• Protons


  • Located in the nucleus
  • Have a positive charge
  • Have a mass of one
• Neutrons


  • Located in the nucleus
  • Have no charge
  • Have a mass of one - similar to the proton
• Electrons


  • Very small: 1/1840 (have basically NO mass)
  • Orbit the nucleus of the atom
  • Have a negative charge
  • In a neutral atom, there are the same number of protons and electrons
• Electron configuration


  The arrangement of electrons in shells
• Electron shells


  • 1st shell - max 2
  • 2nd shell - max 8
  • 3rd shell - max 8/18
  • 4th shell - max 32
• Valence shell


  The outermost shell of an atom, an atom is much more stable if it can completely fill this shell with electrons
• Valence electrons


  Electrons in the outermost shell
• Period


  Shown by the number of notations in the electronic configuration, indicates the number of shells of electrons the atom has
• Group


  Shown by the last notation, indicates the number of outer electrons the atom has
• Elements in the same Group have the same number of outer shell electrons
• Electromagnetic force


  The force that holds all the parts of an atom together, the attraction between the positive protons in the nucleus and the negative electrons orbiting around the nucleus
• Properties of subatomic particles

  • Mass
  • Electrical charge
• The atoms of an element contain equal numbers of protons and electrons and so have no overall charge
• Atomic number


  The number of PROTONS in the nucleus of an atom of an element, used to identify the element from the Periodic Table
• Atomic number


  • Carbon has 6 protons, atomic number 6
• Identifying elements from atomic number

  1. Atomic number 7 - Nitrogen: 7 protons

  2. Atomic number 20 - Calcium: 20 protons

  3. 15 protons - Phosphorus: Atomic number 15

  4. 4 protons - Beryllium: Atomic number 4

  5. Argon - Atomic number 18; 18 protons

  6. Sulfur - Atomic number 16; 16 protons
• Atomic mass number/Nucleon number

  Includes the number of protons and neutrons, since they are the two largest particles in the atom
• Calculating number of neutrons

  Number of neutrons = Atomic mass number - Atomic number
• Atoms


  • Helium: Mass number 4, Atomic number 2, 2 neutrons
  • Fluorine: Mass number 19, Atomic number 9, 10 neutrons
  • Strontium: Mass number 88, Atomic number 38, 50 neutrons
  • Zirconium: Mass number 91, Atomic number 40, 51 neutrons
  • Uranium: Mass number 238, Atomic number 92, 146 neutrons
• Periodic Table


  Used to identify elements, provides atomic number and element symbol
• Atoms have an equal number of protons and electrons and are neutral
• Ion


  A charged particle
• Isotope


  Atoms of the same element that differ in their mass number (number of protons and neutrons)
• Isotopes


  • Virtually identical in their chemical reactions
  • Uncharged neutrons make no difference to chemical properties but do affect physical properties like melting point and density
  • Natural samples of elements are often a mixture of isotopes
• Isotopes of carbon


  • Carbon-12 (6 protons, 6 neutrons)
  • Carbon-13 (6 protons, 7 neutrons)
  • Carbon-14 (6 protons, 8 neutrons)
• Isotopes of hydrogen


  • Hydrogen-1 (1 proton, 0 neutrons)
  • Deuterium (1 proton, 1 neutron)
  • Tritium (1 proton, 2 neutrons)
• Relative atomic mass (RAM)

  Calculated from the mass number and relative abundances of all the isotopes of a particular element
• Calculating RAM


  • Chlorine: RAM = (75 x 35) + (25 x 37) / 100 = 35.5
  • Lithium: RAM = (7.5 x 6) + (92.5 x 7) / 100 = 6.9
  • Magnesium: RAM = (78.6 x 24) + (10.1 x 25) + (11.3 x 26) / 100 = 24.3
• Types of isotopes


  • Radioactive
  • Non-radioactive
• Radioactive isotopes


  • Unstable due to imbalance of neutrons and protons, causing the nucleus to decay over time through nuclear fission and emit radiation
• Radioactive isotopes


  • Tritium
  • Carbon-14
• Non-radioactive isotopes


  Stable atoms that differ only in their mass
• Uses of radioactive isotopes


  • Medical uses
  • Industrial uses
• Medical uses


  • Treating cancer with cobalt-60
  • Medical tracers using Technetium-99
  • Sterilizing medical instruments and materials using gamma rays
• Industrial uses


  • Radioactive dating using carbon-14
  • Detecting leaks in gas/oil pipes using Sodium-24
  • Nuclear power plants using uranium-235