Periodic Trends

1. Electron Configuration
   The periodic table can be divided into sections, or "blocks" depending upon the sublevels that can be filled with electrons

   "s" block

   groups IA and IIA (these fill s¹ and s²)
   note: He is also included as an s²)

   "p" block

   groups 3A,4A,5A,6A,7A and 0

   "d" block

   transition metals

   "f" block

   INNER transition metals (Lanthanoids and Actinoids)

2. Atomic Size
   • the atomic radius is equal to 1/2 the distance between the nuclei of two like atoms
   • Increases as you move down a group and to the left across a period
     increases toward francium
3. Ionization energy
   • the energy required to remove one electron from a gaseous atom
   • increases as you move up a group and to the across a period
     increases towards Fluorine (don't usually consider Noble Gases in trends as they are inert)
   • is a result of nuclear shielding (inner levels of electrons help shiled the outer electrons and the nucleus from each other) remaining constant as you move across a period and the charge on the nucleus becoming greater as you move from left to right across a period
4. Ionic Size
   • positive ions are smaller than the neutral atoms from which they were produced ( gives up electron(s); condenses because of net positive charge)
   • negative ions are larger than the neutral atoms from which they were produced (gains electron(s); expands because of net negative charge)
5. Electronegativity
   • is the tendency for the atoms of the element to attract electrons when they are chemically combined
   • increase as you move up a group and to the right across a period
   • increases toward Fluorine