2.  A pure substance that cannot be broken down or separated into simpler substances.  Made up of one kind of atom.  More than 115 elements known.

3.  Elements are represented by an internationally agreed upon system of symbols  Consists of one or two letters.  Either a single upper case  Hydrogen = H  Or a 1 Upper and 1 lower case  Helium = He

4. Hydrogen =_____Sodium =_____ Potassium=_____ Magnesium =_____ Calcium=_____ Iron =_____ Nickel =_____ Copper =_____ Zinc =_____ Carbon =_____ Nitrogen=_____ Oxygen =_____ Helium=_____ Neon =_____ Chlorine =_____ Silicon =_____ Silver =_____ Gold =_____ Mercury =_____ Lead =_____

5.  Organizes elements according to their physical and chemical properties.  Developed by Dmitri Mendeleev in 1867.

6.  1. organizing known elements according to properties and characteristics  2. recognizing the need to leave spaces for elements not yet discovered

7.  name, symbol, atomic number and atomic mass.