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. Mark a period, group, and the metal, nonmetal, metalloid areas of the periodic table

Aristotle 4 Elements Fire, Water, Air, Earth

14 elements were known

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 and made it into table form to help his students. Elements with similar properties were put into the same column.

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

THE PERIODIC TABLE Dmitri Mendeleev ( )

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.”

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

 Can be hammered or bent without breaking

 The way light interacts with a surface (how it shines)

 Ability to conduct heat and electricity

 Will see bubbling

 Located to the left of the staircase line  Characteristics  Lose electrons to form + ions (cations)  Metallic luster (silver or grayish white)  Malleable  Good conductors  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  Brittle  No reaction with acid  Most reactive nonmetal = F (fluorine)

 Located on and below the staircase line except At, Po and Al.  Characteristics:  Tend to gain or lose electrons  Have properties of metals and nonmetals  Semi-conductors