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Periodic Table
History & Classification
Mendeleev’s Periodic Table-1869
Dmitri Mendeleev•Organized by increasing atomic mass
•Elements with similar properties are grouped together
•Predicted properties of undiscovered elements
Stowe Periodic Table
A Spiral Periodic Table
““Mayan” Mayan” Periodic Periodic
TableTable
Henry Mosely (1913, British)
• Organized elements according to atomic number
• Resolved discrepancies in Mendeleev’s arrangements
The Periodic TableThe Periodic Table
Period
Group or family
PeriodGroup or Family
Roman Numeral = Valence electrons
Periods and Groups
• Horizontal Rows • Periods• Numbered 1-7
• Groups or Families• groups contain elements with similar properties in vertical columns.
Group Numbers
• use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements.
• also use numbers 1-18 to the columns from left to right
Periods and Groups
Several groups of representative elements are known by common names.
Names of Some Representative Elements
Easily lose valence electron (Reducing agents)
React violently with water Large hydration energy React with halogens to
form salts
The Properties of a Group:
the Alkali Metals
Properties of Metals
Metals are good conductors of heat and electricity
Metals are malleable
Metals are ductile
Metals have high tensile strength
Metals have luster
Examples of Metals
Potassium, K reacts with water and must be stored in kerosene
Zinc, Zn, is more stable than potassium
Copper, Cu, is a relatively soft metal, and a very good electrical conductor.
Mercury, Hg, is the only metal that exists as a liquid at room temperature
Properties of Nonmetals
Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element. Nonmetals are poor conductors of heat and electricity Nonmetals tend to be brittle Many nonmetals are gases at room temperature
Halogens
Group 7A(17) the halogens, includes chlorine, bromine, and iodine.
Examples of Nonmetals
Sulfur, S, was once known as “brimstone”
Microspheres of phosphorus, P, a reactive nonmetal
Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure
Properties of Metalloids
Metalloids straddle the border between metals and nonmetals on the periodic table.
They have properties of both metals and nonmetals. Metalloids are more brittle than metals, less brittle than most nonmetallic solids Metalloids are semiconductors of electricity Some metalloids possess metallic luster
Silicon, Si – A Metalloid
Silicon has metallic luster Silicon is brittle like a nonmetal Silicon is a semiconductor of electricity Other metalloids include:
Boron, B Germanium, Ge Arsenic, As Antimony, Sb Tellurium, Te