Chmstry

• Johann Wolfgang Döbereiner


  1829
• Triads


  Groups of three elements based on their chemical properties
• Döbereiner observed that many elements could be grouped into "triads" based on their chemical properties
• Jean-Baptiste Dumas


  1859
• Dumas extended Döbereiner's triads into families of elements in fours (F, Cl, Br, and I; Mg, Ca, Sr, and Ba)
• John Alexander Reina Newlands


  1864
• Law of Octaves


  Newlands arranged the known elements by increasing atomic mass along horizontal rows seven elements long
• Newlands' discovery won him the Davy medal, awarded by the Royal Society of London
• Dmitrij Ivanovic Mendeleev


  1869
• Mendeleev assembled detailed descriptions of more than 60 elements and used John Newlands' grouping to organize the elements into what is now known as the periodic table
• Lecoq de Boisbaudran


  November, 1875
• Lecoq de Boisbaudran discovered one of the predicted elements (eka-aluminum which he named Gallium), showing that Mendeleev's ideas were taken seriously
• Mendeleev's Law


  The physical and chemical properties of elements are a periodic function of their atomic masses
• Periods


  The elements arranged in a series of rows
• Group or Family


  Each vertical column
• Julius Lothar Meyer


  1870
• Meyer was able to develop a periodic table and made the same conclusion as Mendeleev, but his table only consisted of 28 elements and did not include predictions of undiscovered elements
• Sir William Ramsay and Lord Rayleigh


  1894
• Ramsay and Rayleigh discovered the noble gases and they were added to the periodic table as group O
• Helium, the second-most abundant element in the Universe, wasn't found on Earth until 1895
• Henry Moseley


  1914
• Moseley labeled the elements with atomic numbers based upon the number of electrons in an atom rather than on their atomic mass
• Modern Periodic Table


  The periodic table based on modern periodic law
• Series

  The rows of the periodic table
• Period


  Tells the highest level present in a given element
• Families or Groups of Element in the Modern Periodic Table

  • Group IA (Alkali Metals)
  • Group IIA (Alkaline Earth Metals)
  • Group IIIA (Boron Group)
  • Group IVA (Carbon Group)
  • Group VA (Nitrogen Group)
  • Group VIA (Chalcogens)
  • Group VIIA (Halogen)
  • Group VIIIA (Noble Gases or Inert Gases)
  • Group B (Transitional Metals)
  • Lanthanides
  • Actinides
• In North America, the s-p blocks are known as representatives and the d block is known as Transition Metals
• In Europe, the left side of the periodic table is the A group and the right side is the B group
• The International Union of Pure and Applied Chemistry (IUPAC) proposed a system where they number the groups 1-18 with no A's and B's
• Periodic Trends


  The elements in the periodic table are arranged in such a way that there are patterns describing some of their chemical properties
• Atomic Radius


  Measured using the distance between two nuclei of adjacent atoms of the same element and dividing the distance by 2, expressed in nanometers
• Nuclear Charge


  Given by the positively charged proton
• Ionization Energy


  The minimum energy required to remove an electron from a gaseous atom at its ground state, also called ionization potential
• Metallic Property


  Increases from right to left and also increases when going down the group
• Electron Affinity


  The tendency of an atom to accept an electron, dealing with the energy absorbed or released when an electron is added to a neutral gaseous atom in its ground state
• Electronegativity


  The measure of the ability of an atom to attract electrons to itself
• Aufbau Principle (Building up Principle)

  Electrons enter and fill up the lower orbitals before going to higher energy orbitals
• Pauli's Exclusion Principle


  Each orbital can accommodate a maximum of two electrons, and these electrons must have opposite spins
• Hund's Rule


  Electrons must occupy orbitals one at the time before pairing will occur in the same energy orbital
• Writing Electron Configurations


  1. First, write the energy level (the period)

  2. Then, write the subshell to be filled

  3. Then, write the superscript—the number of electrons in that subshell