The Periodic Table SONG

J.W. Dobereiner (1780-1849)J.W. Dobereiner (1780-1849)• discovered the existence of

families of elements with similar chemical properties

• classified elements based on classified elements based on “triads”“triads”– Li Ca S Cl Mn

– Na Sr Se Br Cr

– K Ba Te I Fe

• all elements could not be all elements could not be grouped this waygrouped 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

Main classes of elements

• 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

Stop for Day 1 when shown with Periodic Table video

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

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 results in a positively charged ion (cations) with a 1+ 1+ chargecharge

Chemical Families or Groups

http://www.microchem.de/elec000a-k.JPG

Alkaline Earth Metals• harder and more dense than alkali metals• not as reactive as the alkali metals• characterized by the characterized by the lossloss of two electrons of two electrons

– results in a positively charged ion (cations) with a results in a positively charged ion (cations) with a 2+ 2+ chargecharge

Transition Metals (Elements)• display typical metallic characteristics ductile– malleable, shiny, ductile– malleable, shiny,

conductivityconductivity• form a number of positively charged ions (cations form a number of positively charged ions (cations +1 +2 +3 +4+1 +2 +3 +4))• can share or give away valence electrons to make lots of different

compounds

Halogens• characterized by characterized by gaininggaining one electron one electron• results in a negatively charged ion (anion) with a results in a negatively charged ion (anion) with a 1-1- charge charge

• Form diatomic molecules -- (F2 Br2 I2 Cl2 )

• Fluorine is the most reactive of the elements

Noble Gases

• mostly unreactive due to completely full mostly unreactive due to completely full ss and and pp orbitals orbitals

• 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 can form cations or anions depending on the

conditions / elements combined withconditions / elements combined with

Rare Earth or Inner Transitional Elements

• many are synthetically produced• composed of the lathanoid and actinoid series• have been separated from the others to make the

table not as wide• used in the nuclear industries, metallurgy,

ceramics, electrical components…