Minooka-Elements Periodic Trends
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Minooka-Elements Periodic Trends






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Minooka-Elements Periodic Trends Minooka-Elements Periodic Trends Presentation Transcript

  • The Elements Periodic Trends
  • Where did the elements come from?
    • Naturally-from the centers of the stars
      • Technetium, Promethium, Neptunium are not found on earth but have been detected in the spectra of stars
    • Synthetically-made by cyclotrons and synchrotrons
  • Nuclear Reactions
    • Fusion is the nuclear reaction that creates newer and larger elements from simpler elements
    • Nuclear Fusion reactions can only take place under conditions of extreme heat (such as the conditions found in stars) where the kinetic energy of the particles is so great (high temperature) that it can overcome the repulsion between positively charged protons
  • Big Bang
    • 12-16 billion years ago the entire universe could fit on the head of a pin
    • Huge, violent explosion that occurred within a split second (the big bang)
    • Immediately afterwards temperatures were in the millions of Kelvins (extremely high kinetic energy)
  • Matter as we know it…
    • At extremely high temperatures matter existed as energy only
    • E=mc 2
    • Universe cooled as it expanded
    • As it cooled the energy converted to matter in the form of electrons, protons, and neutrons
  • Nebula-the birthplace of stars
  • More Matter…
    • As the Universe continued to cool the particles formed the first atoms
    • All Hydrogen
    • The H accumulated and formed first generation stars
    • Nuclear reactions took place in the centers of stars forming the elements
  • Natural States of the Elements on Earth
    • Most are found in compounds
    • Few are found as pure elements
      • Gold, silver, copper, platinum relatively inactive and found in pure states
      • Francium and astatine only found in minute amounts
      • Transuranium elements are synthesized and are not naturally occurring
  • Periodic Trends and Definitions
    • Periodic Trends arise from the arrangement of the periodic table in periods, and groups that have similar chemical and physical properties
    • A trend is a predictable change in a property towards a particular direction
    • Properties include electronegativity, ionization energy, atomic radius, density, melting point, boiling point
  • Electronegativity
    • The ability of an atom to attract electrons to itself (electron affinity)
    • A calculated value based on the attraction of shared electrons to a particular atom in a chemical bond
  • Ionization Energy
    • The energy needed to remove an outer electron from an atom (in the ground state, gas phase)
    • Calculated as the minimum energy required to be absorbed by the electron/atom in order to remove an electron from an isolated atom in it’s ground state
  • Atomic Radius
    • The volume occupied by the electrons surrounding the nucleus
    • Difficult to determine
    • Usually determined for atoms that are chemically bonded
    • Defined as 1/2 the distance between the nuclei of the atoms on a molecule
    • Called the bond radius
  • Density
    • Mass per unit volume
    • Usually determined at ambient temperatures (20 o C)
    • Determined for the most thermodynamically stable allotrope
    • Often in g/cm 3
  • Melting Point/Boiling Point
    • Melting point is the temperature at which the solid and liquid phases coexist in equilibrium (at a standard pressure)
    • Boiling Point is the temperature at which the vapor pressure of a liquid is equal to the external atmospheric pressure at 1 atm