Periodic Table History

History of the Periodic Table: At the conclusion of our time together, you should be able to: List one of the earliest contributors to discovery of the elements Explain triads and who developed this table of the elements Explain the law of octaves and who developed this table of the elements Explain the first real periodic table and who developed this table of the elements Show a period, group, and the metal, nonmetal, metalloid areas of the periodic table

Aristotle 4 Elements Fire, Water, Air, Earth ~350 B.C.- Aristotle 4 Elements Fire, Water, Air, Earth

By 1700 - 14 elements were known

Antoine Lavoisier wrote the first extensive list of 33 elements. ~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 weight was between that of Cl & I. He called these groups triads.

Other Triads of Dobereiner: Ca, Sr , Ba S, Se, Te Li, Na, K

1864 - John Newlands (English Chemist) arranged the now known 62 elements from lightest to heaviest. He also noticed that every 8th element had similar chemical and physical properties. Their properties were repeating. This became known as Newland’s Law of Octaves (based on the 8 notes of the musical scale) Li Be B C N O F Na Mg Al Si P S 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. He was considered the Father of the Modern Period Table! **He left blanks where elements seemed to be missing.

Mendeleev (cont.) 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.) This gave rise to the original Periodic Law: properties of the elements are a periodic function of their atomic masses.

The Periodic Table Dmitri Mendeleev (1834 - 1907)

1913 - Henry Moseley (English Chemist and student of Ernest Rutherford) arranged elements by atomic number 9# of protons and also # of electrons). This gave rise to a new (modern)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? 117 118 elements have been identified 82 90 (Tc #43 is excluded) elements occur naturally on Earth Examples: gold, aluminum, lead, oxygen, carbon 35 28 elements have been created by scientists Examples: technetium, americium, seaborgium

Periodic Table Terminology Period/Series = horizontal rows  Group/Family = vertical columns (top to bottom)

Metals Located to the left of the stairstep 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 stairstep line Characteristics: Tend to gain electrons to form negative ions (anions) Dull Poor conductors of heat and electricity Good insulators Brittle Most reactive nonmetal = F (fluorine)

Metalloids Located above and below the stairstep line except At, and Al (and sometimes Po). Characteristics: Tend to gain or lose electrons Shiny and dull Good and poor conductors of heat and electricity Malleable and brittle

History of the Periodic Table: Let’s see if you can: List one of the earliest contributors to discovery of the elements Explain triads and who developed this table of the elements Explain the law of octaves and who developed this table of the elements Explain the first real periodic table and who developed this table of the elements Show a period, group, and the metal, nonmetal, metalloid areas of the periodic table