Periodic Table History History of the Periodic Table
Periodic Table History
History of the Periodic Table: At the conclusion of our time together, you should be able to: 1. List one of the earliest contributors to the discovery of the elements 2. Explain triads and who developed this table of the elements 3. Explain the law of octaves and who developed this table of the elements 4. Explain the first real periodic table and who developed this table of the elements 5. Show the period, the group, and the location of metal, nonmetal, metalloid areas of the periodic table
~350 B. C. Aristotle 4 Elements Fire, Water, Air, Earth
By 1700 14 elements were known
~1789 Antoine Lavoisier wrote the first extensive list of 33 elements.
1829 Johann Dobereiner (German Chemist) noticed that Br, Cl, and I had similar properties and that Br’s atomic mass was between that of Cl & I. He found three other groups with similarities. He called these groups triads.
Other Triads of Dobereiner: Cl, Ca, S, Li, Br, Sr , Se, Na, I Ba Te K
1864 John Newlands (English Chemist) arranged the now known 62 elements from lightest to heaviest. He also noticed that every 8 th element had similar chemical and physical properties. Their properties were repeating. This became known as Newland’s Law of Octaves. Li Na Be Mg B Al C Si N P O S F Cl
1869 Dmitri Mendeleev (Russian Chemist) organized the elements by atomic mass also but made it into table form to help his students. Elements with similar properties were put into the same column. Considered the Father of the Modern Period Table!
Mendeleev (cont. ) He left blanks where elements seemed to be missing. There were places where heavier elements were put before lighter elements because of properties: Te – I Co – Ni Ar – K He felt the mistake was in measuring the mass and this would be corrected with further research.
The Periodic Table Dmitri Mendeleev (1834 - 1907)
Mendeleev (cont. ) This gave rise to the Periodic Law, “Properties of elements are periodic functions of their atomic mass. ”
1913 Henry Moseley (English Chemist) arranged elements by atomic number. This gave rise to a New Periodic Law, “Properties of elements are periodic functions of their atomic number. ”
Glenn Seaborg (1912 -1999) Discovered 8 new elements. Only living person for whom an element was named.
The Language of Chemistry The elements, their names, and symbols are given on the PERIODIC TABLE How many elements are there? • 117 elements have been identified • 82 elements occur naturally on Earth • Examples: gold, aluminum, lead, oxygen, carbon • 35 elements have been created by scientists • Examples: technetium, americium, seaborgium
Periodic Table Terminology Periods/Series = horizontal rows Group/Family = vertical columns
Metals Located to the left of the staircase line Characteristics Lose electrons to form + ions (cations) Shiny Malleable Ductile Good conductors of heat & electricity React with acid Most metallic element = Fr (francium)
Nonmetals Located to the right of the staircase line Characteristics: Tend to gain electrons to form – ions (anions) Dull Poor conductors of heat and electricity Good insulators Brittle Most reactive nonmetal = F (fluorine)
Metalloids Located on and below the staircase line except At and Al. Characteristics: Tend to gain or lose electrons Shiny and dull Good and poor conductors of heat and electricity Malleable and brittle
Solids, Liquids and Gases at Room Temp
History of the Periodic Table: Let’s see if you can: 1. List one of the earliest contributors to the discovery of the elements 2. Explain triads and who developed this table of the elements 3. Explain the law of octaves and who developed this table of the elements 4. Explain the first real periodic table and who developed this table of the elements 5. Show the period, the group, be able to locate the metals, nonmetal, metalloid areas in the periodic table
- Slides: 22