PERIODIC TABLE

• The development of the periodic table as we know it today started in 1829 when Johann Dobereiner proposed the model of triads or the law of triads
• Triads


  A set of three elements where the atomic weight of the middle element is approximately equal to the arithmetic mean of the two extreme elements in the set
• Dobereiner's model fails to apply to most of the elements known during his time, proving the model severely lacking
• John Newland's law of octaves was proposed

  1864
• Newland observed that elements are arranged based on their atomic weights, elemental properties seem to repeat every eight elements
• The idea of a periodic table of elements was presented to the world during the time of Julius Lothar Meyer and Dmitri Ivanovich Mendeleev
• The modern periodic table that we know today is arranged based on atomic number, unlike Mendeleev's table which was arranged based on atomic mass
• Periods


  The rows in the periodic table
• Groups or Families


  The columns in the periodic table
• Types of elements in the periodic table

  • Representative elements (Groups 1, 2, 3-17)
  • Transition metals (Groups 3-12)
  • Boron group (Group 13)
  • Carbon group (Group 14)
  • Pnictogens (Group 15)
  • Chalcogens (Group 16)
  • Halogens (Group 17)
  • Noble gases (Group 18)
• Representative elements


  Elements in Groups 1, 2, and 3-17 with their highest s or p orbital incompletely filled
• Alkali metals


  Elements in Group 1 that are highly reactive and possess a single electron in their outermost shell
• Alkaline earth metals


  Elements in Group 2 that have two electrons in their valence shell which they readily lose to form cations with +2 charges
• s block


  Groups 1 and 2 (except H and Be)
• Noble gases


  Group 18 elements that have filled p subshells (except He) and are chemically inert
• Transition metals


  Elements in Groups 3-12 that are generally characterized by partially filled d subshells or those which can give rise to cations with an incomplete d subshell
• d block


  Groups 3-12
• Boron group


  Group 13 elements that all have three electrons in their outermost shell
• Carbon group or crystallogens


  Group 14 elements that are characterized by 4 electrons in their outermost shell
• Pnictogens


  Group 15 elements that all have 5 valence electrons
• Chalcogens


  Group 16 elements that are composed of electronegative nonmetals and metalloids, all of which have 6 electrons in their outermost shell
• Halogens


  Group 17 elements that are famously known as the only group in the periodic table with members existing as gas (fluorine and chlorine), liquid (bromine), and solid (iodine and astatine) at room temperature, and have 7 electrons in their outermost shell
• p block


  Groups 13-18 that are made up of metals, nonmetals, and metalloids
• Group 14 elements


  Characterized by 4 electrons in their outermost shell
• Group 15 elements (pnictogens)


  All have 5 valence electrons
• Aside from nitrogen, pnictogens are solid at room temperature
• Group 16 elements (chalcogens)


  Composed of electronegative nonmetals and metalloids, all have 6 electrons in their outermost shell
• Group 17 elements (halogens)


  • The only group in the periodic table with members existing as gas (fluorine and chlorine), liquid (bromine), and solid (iodine and astatine) at room temperature
  • Have 7 electrons in their outermost shell, readily accept an electron to form anions with a -1 charge
• Groups 13-18


  Collectively known as the p block elements
• p block


  Made up of metals, nonmetals, and metalloids (elements with properties intermediate to both metals and nonmetals)
• Metalloids


  • B
  • Si
  • Ge
  • As
  • Sb
  • Te
• Po and At are irregularly accepted as metalloids, while Al and C are rarely recognized as metalloids</b>
• Because of their unique properties, metalloids are used in the manufacturing of semiconductors
• Lanthanide and actinide series

  Collectively called the f block transition metals due to their incompletely filled f subshells
• Lanthanides


  Rare earth elements, naturally occurring but exist in extremely small amounts (less than 0.001% of the Earth's crust), more abundant than other elements but highly dispersed in the Earth's crust, have incompletely filled 4f subshells or form cations with incompletely filled 4f subshells
• Actinides


  All radioactive, heavy elements that are not naturally occurring, some named after famous scientists, either have incompletely filled 5f subshells or form cations with incompletely filled 5f subshells
• Atomic radius


  • One-half the distance between two adjacent atoms
  • Generally increases down the group and decreases across a period from left to right
• Electronegativity


  • The tendency of an atom to draw shared electrons in a chemical bond towards itself
  • Increases as you approach fluorine (i.e., increases across a period from left to right and decreases down the group)
• Fluorine is the most electronegative element in the periodic table
• Ionization energy


  • The minimum energy required (in kJ/mol) to remove one electron from an isolated atom or molecule
  • Decreases down a group and increases across a period from left to right