Periodic Table History

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 mass was between that of Cl & I. He found three other groups with similarities. He called these groups triads.

Other Triads of Dobereiner: Cl, Br, I 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. 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 and made it into table form to help his students. Elements with similar properties were put into the same column.

Mendeleev (cont.) He left blanks where elements seemed to be missing. He was considered the father of the Modern Periodic Table. There were places where heavier elements were put before lighter elements because of their 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)

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.

Periodic Table Terminology Period/Series = horizontal rows  Group/Family = vertical columns

Metals Located to the left of the staircase line Characteristics Lose electrons to form + ions (cations) Shiny Metallic luster (silver or grayish white) Malleable Good conductors 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 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 Malleable and brittle

Where are Periods, Groups, Metals, Nonmetals, and Metalloids?