applied chem. c3 notes development of the periodic table
TRANSCRIPT
C3-1: Search for a Periodic Table
• 1829 JW Dobereiner (old German guy)– Classified elements into 3 groups• Triads
– Similar properties
Mendeleev’s Periodic Table
• 1869 Russian Chemist• Studied properties of elements• Arranged elements in repeating pattern of
increasing atomic mass
Why this Mendeleev’s table is special!
• Periodicity: Tendency to recur at regular intervals.
• Mendeleev correctly predicted the properties of several undiscovered elements.
• Left blank spaces for undiscovered elements• Formed basis for modern periodic table
Characteristics of Modern PT
• Arranged by atomic number and not atomic mass.– Find where the atomic number increases but
atomic mass decreases.
• Periods (rows)• Groups (columns)
Periodic Law
• Physical and chemical properties of the elements repeat in a regular pattern when they are arranged in order of increasing atomic number
C3 Section 2 Vocabulary
• Period Metalloid• Group Semiconductor• Noble Gas• Metal• Transition metal• Lanthanide• Actinide• Nonmetal
C1 Section 2: Using the Periodic Table
• Periods (rows)– Represent the energy levels electrons can occupy.– Each new period has a new energy level
• Groups (columns)– Sometimes called a family– All elements in a group have similar properties
Physical States and Classes of Elements
• Metals are elements that have luster, conduct heat and electricity, and usually bend without breaking
• Majority of elements
Transition metals
• Elements in groups 3-12• Commonplace: Silver (Ag), Copper (Cu), Iron
(Fe), Zinc (Zn)• Some radioactive• Not as predictable in properties as main group
elements
Inner Transition Metals
• Lanthanides=Atomic numbers 57 (Lanthanum) to 71.– Not naturally abundant on earth– Called “rare earth”– All lanthanides have similar properties
• Actinides=Atomic numbers 90-103– Unpredictable properties
Characteristics of Nonmetals
• Many nonmetals are abundant in nature.• Examples include oxygen and nitrogen that
make of 99% of atmosphere.• Don’t conduct electricity.• Poor conductors of heat.• Brittle when solid.• Many nonmetals are gases at room
temperature.
Metalloids
• Some properties of metals and some properties of nonmetals
• Lie between the border of metals and nonmetals
• Some metalloids are semiconductors
• Silicon (Si), germanium (Ge) and arsenic (As) are metalloids that are semiconductors.
• Look at your phone for uses of semiconductors!