Topic 2, the Periodic Table
Topic 2, the Periodic Table
(Key concepts)


*Elements arranged according to increasing atomic number
*Periods
: Horizontal rows; elements have electrons in the same energy levels; Period 2 elements, for example, have e- occupying the 1st and 2nd energy levels
*Groups: Vertical columns; families; members of a group have the same # of valence electrons, therefore, have similar chemical properties
*Metals on left (malleable, ductile, shiny, good conductors)
*Nonmetals on right (brittle, dull, poor conductors)
*Metalloids along zig-zag line (properties between metallic and nonmetallic)
*Liquids:  Hg and Br
*Gases:  H, N, O, F, Cl, Ne, Ne, Ar, Kr, Xe, Rn
*Solids: all others
*Alkali metals:  Group 1; 1 val e-; so reactive not found alone in nature
*Alkaline Earth metals: Group 2; 2 val e-; so reactive not found alone in nature
*Transition elements (metals): Groups 3 - 12; multiple positive oxidation states; form colored solutions

*Halogens: Groups 17; 7 val e-; so reactive not found alone in nature
*Nobel gases:  Group 18; filled valence e- energy levels; nonreactive
*Electronegativity:  Table S; attraction for e-; nonmetals high and gain val e-; nonmetals gain e- forming (-) ions larger than atom

Image result for electronegativity table

*Ionization energy: Table S; energy needed to remove e-; metals low and readily lose val e-; metals lose e- forming (+) ions smaller than atom

*Atomic radius: Listed on Table S; increase down a group because additional energy levels; decrease across a period because same energy level attracted to stronger (+) nuclei