Periodic Table

• Johann Wolfgang Dobereiner

  • proposed that elements were arranged according to triads
  • Wherein the atomic mass of the middle element is almost equal to the average of the atomic masses of the 1st and 3rd element
• Law of Octaves - proposed by John Newlands

  - elements are arranged according to atomic weight with 8 elements per row/column
• Dmitri Ivanovich Mendeleev - Russian chemist who arranged the elements in order of increasing atomic weight

  The blank space in his periodic table contained 7 periods and 8 groups with blank spaces for yet-to-be discovered elements
• Periodic Law states that the physical and chemical properties of an element is a periodic function to its atomic number
• Henry Moseley - revised Mendeleev's periodic table and re-arranged elements according to its atomic number, This led to the modification of the periodic table.
• Modern Periodic law states that, elements are arranged in order of increasing atomic number
• Periods - there are 7 periods in the periodic table

  - shows the energy levels or electrons
• Groups- there are 18 groups in the periodic table

  - 3 main groups in the periodic table

  • representative elements (G1, G2, G13-18)
  • Transition elements ( G3-12)
  • Inner transition elements (Lanthanides and Actinides)
• IUPAC - International Union of Pure and Applied Chemistry
• Blocks - there are 4 blocks

  - s block (2 electrons)

  - p block (6 electrons)

  - d block ( 10 electrons)

  - f block (14 electrons)
• Period Trends - patterns of change across a period or group
• Atomic radius - The distance between the nucleus and the outermost electron.
• Atomic radius

  • top to bottom is in increasing order
  • left to right is in decreasing order

  
• Ionic radius of a positive ion is smaller than the atomic radius of an elements

  Ionic radius of a negative ion is bigger than the atomic radius of an elemenst

  
• ion that loses electrons and become negative is a Cation

  ion that gains electrons and become positive is Anion
• ionization energy - the energy required to remove one electron from a neutral atom to form a positive ion
• low ionization energy = easier removal of electrons
• Low ionization energy= Alkaline and Alkali Earth Metals

  High ionization energy= non-metals

  Highest ionization energy= noble gases ( due to its no reaction)
• Ionic radius, electron affinity, and electronegativity

  • left to right - increasing
  • top to bottom- decreasing
• Electron Affinity - amount of energy released or absorbed when an electron is added to form anion

  - measurement of the tendency of an atom to form anion
• Electron Affinity

  Cations: Alkaline and Alkali earth

  Anion: Boron, carbon, nitrogen, oxygen and fluorine group
• Electronegativity - ability of an atom to attract electrons
• Metallic Character:

  Metals- left side of staircase (EXCEPT HYDROGEN)

  Metalloids- within staircase

  Non-metals - right side of staircase(WITH HYDROGEN)