2.  Elements are arranged according to atomic number  Number of protons  Not atomic mass

3.  Horizontal row in periodic table  7 total  Period 6 = lanthanoids  Period 7 = actinoids

4.  Vertical column in the periodic table  18 groups  Elements in same group  Same physical and chemical properties  Same number of electrons in last energy level

5.  1 = alkali metals (except for H)  2 = alkaline earth metals  3-12 = transition metals  14 = carbon family  15 = nitrogen family  16 = oxygen family  17 = halogens  18 = noble gases  (unreactive)