19.3 – Periodic Table

Objectives – LT#8-13 Use the periodic table to obtain information. Describe the arrangement of the periodic table. Explain how groups on the periodic table were determined and what similarities exist between elements in the same group. Relate the location on the periodic table to the number of energy levels in an element. Explain the importance of a full valence shell and how that is achieved by noble gases Explain what metals, nonmetals and semi-metals are and where they are located on the periodic table.

Organization of Elements Dmitri Mendeleev Discovered pattern (periodic) when he arranged elements in order of increasing atomic mass Mendeleev made predictions and left blanks in his periodic table as he lined up elements by chemical properties

Mendeleev ’ s Periodic Table PropertyEkasiliconGermanium Atomic mass (amu) Density (g/cc) Melting Point (C)High947 ColorGray

Current Periodic Table Arranged by increasing atomic # and by physical and chemical properties 1913, Henry Moseley improved Mendeleev ’ s periodic table by arranging elements by atomic #

Groups or Families Vertical Columns 18 groups Members of each group have similar properties Some groups are given family names Group 1 = Alkali metals Group 2 = Alkaline earth metals Groups 3-12 = Transition metals Group 17 = Halogens Group 18 = Noble gases

Periods Horizontal Rows Represent the number of energy levels Each energy level can hold a set # of electrons 1 st energy level = 2 electrons 2 nd = 8 electrons Increase # protons and # electrons as you go left to right

Full valence shell Elements become stable by obtaining a full energy shell of electrons H & He are stable with just 2 e- All other elements are stable with 8 e- in outer energy level Valence electrons are used in bonding

Electron dot diagrams Diagram that shows how many valence electrons in outer energy levels Same group = same # bonding electrons

Regions of Periodic Table Metals = Blue squares room temperature Shiny Good conductors

Regions of Periodic Table Non-metals = yellow squares on right side Most are gases Brittle Poor conductors Semimetals = green staircase Properties of metals and non-metals

In-Class Assignment/Homework 19.3 Reinforcement WKT Tomorrow – Directed Reading & Enrichment WKT