Chapter 5 The Periodic table Chemistry Chapter 5 The Periodic table

The Periodic table Most valuable tool to chemists Developed by Dimitri Mendeleev Originally arranged by increasing atomic mass Modern periodic chart is arranged by increasing atomic number http://www.topspeed.tv/mrs.demaree/mendeleev.jpg

Periodic Law Rows are called periods Atomic mass and atomic number increase across a period Columns are called Groups or Families Elements in groups have the same number of valence electrons Elements in the same group also have similar chemical properties The pattern or repeating properties is called PERIODIC LAW

Periodic Trends Families Atomic Radius Ionization energy Electronegativity Reactivity Webshots.com

Atomic Radius As atomic # increases, the increasing # of protons attracts valence electrons more closely to nucleus. Within a period, atomic radius decreases as atomic # increases

Atomic Radius Trends Increases Atomic Radius Decreases

Ionization Energy Energy required to remove an electron from an atom’s outer energy shell. In a period, IE increases as atomic # increases. In a group, IE decreases as atomic # increases

Ionization Energy Trends IE Increases IE Increases

Electronegativity Ability of an atom to attract electrons to itself in a compound. EN increases from lower left to upper right of periodic table. (similar to ionization energy)

Electronegativity Trends EN Increases sesaercnI NE

Reactivity How readily a substance combines chemically w/another substance Elements w/out full set of valence electrons tend to react. Elements w/full set tend NOT to react. (Noble Gases)

Noble Gases Noble Gases

Classes of elements Metals- on left of periodic table Nonmetals- right Metalloids- in between Titanium Helium Germanium