CHEMICAL PERIODICITY

• Periodic Trends

  • properties of elements that behav e predictably as we go vertically or horizontally through the periodic table
• The Periodic Trends consists of:

  • Effective Nuclear Charge
  • Atomic Size
  • Ionic Size
  • Ionization Energies
  • Electron Affinities
  • Metallic Property
• Effective Nuclear Charge

  • the net electric field by electrons in various regions in the atom with respect to the nucleus is treated as a charged point
  • Zef = Z−S, S is the screening constant
  • From left to right of periodic table, Zeff increases
  • From top to bottom of periodic table, Zeff increases
• Atomic Radius

  • Within each group, atomic radius tends to increase from top to bottom (increase in the value of n)
  • Within each period, atomic radius tends to decrease from left to right (increase in the value of Zeff)

  
• Ionic Radius

  • cations are smaller than parent atoms while anions are larger than parent atoms (change in the value of Zeff)
  • Within each row (same charge), ionic radius tends to increase from top to bottom (increase in value of n)
• Ionization Energy

  • minimum energy needed to remove an electron from the ground state of the isolated gaseous atom or ions

  1. WIthin each period of the periodic table, Ionization Energy generally increases with increasing atomic number (increase in Zeff)
  2. Within each group of the periodic table, IE generally decreases with increasing atomic number (electrons become farther away from the nucleus)
  3. Range of IE values are greater for s- and p-block elements compared to d-block elements
• Electron Affinity

  • increases upward across periods of a periodic table for the groups and from left to right,
  • because the electrons added to the energy levels get closer to the nucleus, making the nucleus and its electrons more attractive.
• Metallic Properties

  • the elements are grouped in the periodic table based on metallic properties as shown below:

  A) metals

  B) metalloids

  C) nonmetals

  
• Metals, Non-metals, & Metalloids

  A) lose

  B) gain

  C) lose or gain

  D) cations

  E) anions

  F) both

  G) basic

  H) acidic

  I) amphoteric

  J) base

  K) acid

  L) both

  M) good

  N) poor

  O) Dual

  P) good

  Q) poor

  R) dual

  
• Characteristic Properties of Metals and Nonmetals

  A) Metals

  B) Nonmetals

  
• Ion - charged atom

  • Anion - "negatively"-charged; gain electrons;
  • electrons > protons
  • Cation - "positive"-charged; loss of electron;
  • electrons < protons
• Ionization energy

  • energy required to remove an electron from an atom
• Electron Affinity

  • energy released when an electron is added to an atom
• Electronegativity

  • ability to attract electrons
  • e.g. Cl has high electronegativity since it lacks one electron in its outermost shell thust it attracts an electron to make it more stable: it usually has a -1 charge (Cl); increases as atomic size decreases