- the elements on the two rows which appearunderneath the main body of the periodictable

- These elements are very reactive and very unstable.Often these elements can only be made in alaboratory and they they usually have radioactiveproperties

- Some examples of this are Cerium, Dysprosium,Erbium, Europium, Gadolinium, Holmium,Lutetium

- The two scientists who had the biggestimpact were Dmitri Mendeleev and LotharMeyer.

- Mendeleev arranged the elements in hisperiodic table in order of increasing atomicmass

- Meyer used atomic weights to arrange 28elements into 6 families that bore similar chemicaland physical characteristics, leaving a blank foran

- example: every element in a group has the samenumber of valance electrons, and each element willhave a larger mass and number than the elementbefore it.

- basically it states that elements follow apattern which controls theircharacteristics

- This is the principle that states that properties ofthe elements recur periodically as their atomicnumber increases.

- elements can be classifies by their mass, numberof protons, number of neutrons, and commoncharacteristics

- classes can be separated by the number ofvalance electrons that they have, this effects theircharacteristics

- classifications include number of valanceelectrons, types of groups and periods, and atomic numbers

- Non-metallic elements

- Solid Halogens: Astatine and Iodine

- Liquid Halogens: Bromine

- Gas: Fluorine and Chlorine

- They are reactive, electropositive, divalent metals,and form basic oxides that react with water toform comparatively insoluble hydroxides.

- This is are the second group

- beryllium, magnesium, calcium,strontium, barium, and radium

- They are found on group one, which isthe far left column on the periodictable.

- They are very reactive, electropositive,monovalent metals forming strongly alkalinehydroxides.

- Some of which include sodium,potassium, rubidium, cesium, andfrancium

- They were long believed to be totally unreactivebut compounds of xenon, krypton, and radon arenow known.

- They are the the farthest mostright group on the periodic table.

- Some noble gases include helium,neon, argon, krypton, xenon, andradon

- there are many different transitions metals butsome examples are iron, manganese, chromium,and copper.

- These metals take up multiple groups on theperiodic table and can be found in columns 4through 12.

- Chemically they show variable valence and astrong tendency to form coordination compounds,and many of their compounds are colored.