1. List one of the earliest contributors to 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 a period, group, and the metal, nonmetal, metalloid areas of the periodic table

Aristotle 4 Elements Fire, Water, Air, Earth

14 elements were known

Antoine Lavoisier wrote the first extensive list of 33 elements.

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.

Cl, Br, I Ca, Sr, Ba S, Se, Te Li, Na, K

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. LiBeBCNOF NaMgAlSiPSCl

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. Original Periodic Law: properties of the elements are a periodic function of their atomic masses. Considered the Father of the Modern Period Table!

He left blanks where elements seemed to be missing. There were places where heavier elements were put before lighter elements because of properties: Te – ICo – NiAr – K He felt the mistake was in measuring the mass and this would be corrected with further research.)

Dmitri Mendeleev ( )

Henry Moseley (English Chemist) arranged elements by atomic number. This gave rise to a new (modern)Periodic Law, “Properties of elements are periodic functions of their atomic number.”

Discovered 8 new elements. Discovered 8 new elements. Only living person for whom an element was named. Only living person for whom an element was named.

The elements, their names, and symbols are given on the PERIODIC TABLE The elements, their names, and symbols are given on the PERIODIC TABLE How many elements are there? How many elements are there? 118 elements have been identified 91 (Tc #43 is excluded) elements occur naturally on Earth Examples: gold, aluminum, lead, oxygen, carbon 27 elements have been created by scientists Examples: technetium, americium, seaborgium

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

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)

Located to the right of the staircase line Characteristics: Tend to gain electrons to form – ions (anions) Dull Poor conductors of heat and electricity Brittle Most reactive nonmetal = F (fluorine)

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

1. List one of the earliest contributors to 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 a period, group, and the metal, nonmetal, metalloid areas of the periodic table