Periodic Table

Physical Science

A) Early Attempts • In the 1800’s, chemists tried to organize the elements using

their chemical and physical properties• They laid the foundation for the modern periodic table• Some chemists notices that certain properties repeated every

eighth element, but this only worked for the first twenty elements

• Early tables organized the elements by their atomic mass, this presented some issues with elements such as – Ar and K– Co and Ni– Te and I– Th and Pa

• By the early 1900’s the table was arranged in order of Atomic Number rather than mass, the way it is today

B) Dmitri Mendeleev

• Father of the Periodic Table• Published in 1869 a table with the elements

arranged by atomic mass• Left gaps for elements that had not been

discovered yet• Because his predictions about unknown

elements were so darn close, he is credited with the creation of the periodic table

Property Mendeleev’s Prediction Observed Properties

Atomic Weight 72 72.59Density 5.5 5.35Specific Heat 0.305 0.309Melting point High 947 CColor Dark gray Grayish whiteFormula of oxide XO2 GeO2

Density of oxide 4.7 4.70Formula of Chloride XCl4 GeCl4

Boiling point of chloride A little under 100 84 C

Predictions About the Undiscovered Element- Germanium

Sculpture of Mendeleev in Slovakia- Talk about getting your Nerd On!!!!!

C) Periodic Table Geography-Horizontal Rows on the table are called Periods

- Periods represent energy levels in an atom-Vertical Columns on the table are called Families or Groups

- Each element in a family has the same number of valence electrons

- Elements in a group have similar chemical and physical properties

Periodic Law- says that when arranged by atomic number that certain traits occur periodically, thus creating families, certain family have particular names

Group 1 – Alkali Metals * highly reactive metals that do not occur freely in nature

-must be stored either in wax or oil to protect * 1 valence electron in the outermost shell* often soft metals, but are good conductors of electricity and heat*malleable and ductile*low melting points*form very strong basic solutions

Group 2- Akaline Earth Metals*also highly reactive metals* 2 valence electrons in the outermost shell* called earth metals because of their extremely high melting points*burn reddish colors in flame tests

Groups 3-12 Transition Metals

*38 elements total*Good conductors, malleable and ductile* these elements the gain or lose electrons differently based upon the

particular chemical reaction

Group 17 –Halogens*non-metallic *seven valence electrons*elements are found in three different phases-solids, liquids and gas*highly reactive, found in lots of compounds

Group 18 – Noble Gases*not very reactive*8 valence electrons in outermost shell, making them stable*all of them are gasses

Groups 14-16 – Non-metals also include groups 17-18*Poor conductors of heat and electricity*very brittle, dull colored*can be solids or liquids*tend to form acidic solutions*lower densities than metals*are highly electronegative, tend to steal electrons from other atoms

Metalloids – line the transition between metals and non-metals*have properties similar to both metals and non-metals*elements 5, 14, 32, 33, 51, 52, 84, 85

Rare Earth Elements* compose the lanthanide and actinide series

-the two lonely rows at the bottom*total of 30 elements*are all metals*most are man-made*highly electrically conductive*mainly formed in complex minerals, which made them seem rare