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

http://www.cartage.org.lb/en/themes/sciences/chemistry/generalchemistry/elements/periodic/formulated/mendelev.gif

Mendeleev’s Periodic TableProperty Ekasilicon Germanium

Atomic mass (amu)

72 72.59

Density (g/cc) 5.5 5.35

Melting Point (C) High 947

Color Gray Gray

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 #

https://reich-chemistry.wikispaces.com/file/view/moseley.jpg

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 1st energy level = 2 electrons 2nd = 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

http://www.roymech.co.uk/images14/lewis_elements.gif

Regions of Periodic Table

Metals = Blue squares Solids @ 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