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SONG. The Periodic Table. J.W. Dobereiner (1780-1849). discovered the existence of families of elements with similar chemical properties classified elements based on “triads” Li Ca S Cl Mn Na Sr Se Br Cr K Ba Te I Fe all elements could not be grouped this way.
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SONG The Periodic Table
J.W. Dobereiner (1780-1849) • discovered the existence of families of elements with similar chemical properties • classified elements based on “triads” • Li Ca S Cl Mn • Na Sr Se Br Cr • K Ba Te I Fe • all elements could not be grouped this way
Dmitri Mendeleev (1829-1869) • Russian chemist and teacher • organized a “Periodic Table” (only knew about 63 elements at the time) based on increasing atomic mass • the properties of elements had something to do with their mass • he even left empty spaces to be filled in later
Metals • about 80% of elements are metals • good conductors of heat and electricity • shiny • have high melting points • ductile • malleable • will corrode (rust) in water or air • tendency to lose electrons
Nonmetals or gases • located to the right of the “zig-zag line” in the periodic table • often are different from one another • dull • do not conduct heat and electricity • not malleable nor ductile • tendency to gain electrons
Metalloids • only 7 elements on the “zig-zag line” • have some characteristics of both metals and nonmetals
Design of the Table • Groups are the vertical columns. • elements have similar, but not identical, properties • most important property is that they have the same # of valence electrons
Hydrogen (H) and helium (He) are special elements. Hydrogen can have the talents and electrons of two groups, one and seven. To scientists, hydrogen is sometimes missing an electron, and sometimes it has an extra. Helium is different from all of the other elements. It can only have two electrons in its outer shell. Even though it only has two, it is still grouped with elements that have eight (inert gases).
Periods are the horizontal rows • do NOT have similar properties • however, there is a pattern to their properties as you move across the table
Chemical Families or Groups Alkali Metals • soft metals • most reactive of the metals because they all lose one valence electron very easily • results in a positively charged ion (cations) with a 1+ charge
Alkaline Earth Metals • harder and more dense than alkali metals • not as reactive as the alkali metals • characterized by the loss of two electrons • results in a positively charged ion (cations) with a 2+ charge
Transition Metals (Elements) • display typical metallic characteristics ductile– malleable, shiny, conductivity • form a number of positively charged ions (cations+1 +2 +3 +4) • can share or give away valence electrons to make lots of different compounds
Halogens • characterized by gaining one electron • results in a negatively charged ion (anion) with a 1- charge • Form diatomic molecules -- (F2 Br2 I2 Cl2 ) • Fluorine is the most reactive of the elements
Noble Gases • mostly unreactive due to completely full s and porbitals • colorless, odorless gases
Mixed Groups • not as similar to each other as other groups • usually named after the first element in the group (B C N O) • can form cations or anions depending on the conditions / elements combined with
Rare Earth or Inner Transitional Elements • many are synthetically produced • composed of the lathanoid and actinoidseries • have been separated from the others to make the table not as wide • used in the nuclear industries, metallurgy, ceramics, electrical components…
