2.3: the periodic table

metals
- conductors (to varying degrees)
- lose electrons
- malleable and ductile (flexible)
- shiny/lustrous
nonmetals
- nonconductors
- gain electrons
- brittle (not malleable or ductile)
- dull in texture/appearance
metalloids/semi-conductors
- bridge metals and non-metals, have qualities of both

metal groups

alkali metals
- have one valence electron (electron in the highest occupied energy level)
- most reactive metal group
alkaline earth metals
- 2 valence electrons
- less reactive than alkali metals
- 2nd most reactive group
transition metals
- multiple charges on ions
- some references refer to these elements as “post-transition metals”
- don’t behave consistently

nonmetal groups

halogens
- 7 valence electrons
- most reactive nonmetal group
noble gases
- 8 valence electrons (highest occupied energy level is full)
- most stable group

periodic table: a systematic organization of the elements
elements are arranged in order of atomic number
the rows of the periodic table (left to right) are called periods
the columns of the periodic table (top to bottom) are called groups or families
elements in the same group have similar properties
periodicity
periodic = cyclical
there is a repeating pattern of reactivities and other properties as we move across the periodic table
metals are on the left side of the periodic table, whereas non-metals are on the right side of the table (except for Hydrogen). metalloids are near the right side but not on the far right.