metals - make up 3/4 of the periodic table, in left/middle part  

• shiny luster
• malleable (can be pounded into thin sheets)/ductile (can be drawn into wires)
• good conductors of heat/electricity
• tend to form cations (have low ionization energies) in aqueous solutions
• compounds of metals w/ nonmetals tend to be ionic
• most metal oxides are basic (form hydroxides when dissolved in water)
• metal oxides w/ acid form salt
• alkali metals (group 1A) - soft metallic solids
  • have the lowest I1 on each row
  • hydride ion - H-; bonds w/ alkali metals to form hydrides
  • reacts exothermically w/ water
  • superoxide - O2-; combines w/ potassium, rubidium, cesium
  • emit certain colors when heated by a flame
• alkaline earth metals (group 2A) - denser/harder than alkali metals
  • less reactive than alkali metals
  • Mg used for lightweight structure alloys because layer of MgO protects it from other chemicals

nonmetals - on right side of periodic table  

• no luster, has various appearances
• poor conductors of heat/electricity
• most nonmetal oxides are acids
• tend to form anions/oxyanions in aqueous solutions
• molecular substances - compounds made up only of nonmetals
• hydrogen - doesn't really belong in a particular group
  • exists as H2 gas in most conditions
  • can be metallic at very high pressures
  • has much higher I1 than other alkali metals (lacks any type of nuclear shielding)
• oxygen group (group 6A)
  • elements change from nonmetal to metal as you go down the group
  • allotrope - different form of same element in same state
  • ozone - O3, less stable than O2
  • sulfur - exists naturally as S8 rings
• halogens (group 7A) - aka "salt formers"
  • melting/boiling points increase as atomic number increases
  • very highly negative electron affinities
  • Cl - most industrially useful halogen
  • forms halide compounds w/ hydrogen
• noble gases (group 8A) - monoatomic nonmetals, gas at room temperature
  • have completely filled s and p subshells
  • very unreactive

metalloids - have properties intermediate between metals/nonmetals  

• have only some metallic properties, but lack others
• many used as electrical semiconductors, integrated circuits