Notes Chapter 5 Book chapter 4-2

I. Development of a Periodic Table *Periodic: repeating according to some pattern. -Mendeleev Table: elements arranged in order of increasing atomic mass.

II. The Modern Periodic Table -Table used today was created by Mosely

A.) New Periodic Law *Periodic Law: the physical and chem. properties of the elements are periodic functions of their atomic #

B.) Columns of the Table *Groups: up and down -have similar but not identical properties

C.) Row of the Table *Period: horizontal row -not alike in properties -1 st element is always a very reactive solid

-last element is always very inactive gas -6 and 7 are rare earth elements.

III. Using the Periodic Table

A.) Metals and Nonmetals *Metals: 1. Good conductors 2. Ductile 3. Malleable -found left of the staircase line

*Nonmetals: 1. Poor conductors 2. Dull surfaces 3. Low melting points -found right of the staircase line.

*Metalloids: 1. Shiny or dull 2. Conduct better than nonmetals.

3. Include boron, silicon, germanium, arsenic, antimony, tellurium. -found along each side of the dark staircase line.

IV. Periodic Properties of the Elements -Certain properties of elements vary in a regular way from left to right across a period.(e- arrangement, reactivity, atomic size, and metallic properties

-valence e-: e- ’ s in the outermost nrg level -valence #: # of e- ’ s that can be gained or lost -oxidation #: # of e- ’ s that can be gained or lost

-L-R valence # ’ s 1, 2,3,4,3, 2,1,0 -L elements lose e- easily -R tend to gain e- easily -L-R atom size decreases -L-R elements become less metallic in nature