1. Organizing the Elements

2.  Early scientists tried to group elements according to their properties This process proved to be very difficult and confusing  Scientists then revealed that elements could be arranged in order of increasing atomic mass

3. Atomic Mass: is the mass of one atom of an element Measured in atomic mass unit (amu)  Dmitri Mendeleev organized the elements based on atomic mass and patterns in the properties of elements to form the first periodic table  Over the years his table has been modified into today’s version of the periodic table

4. The Periodic Table The Periodic table is designed to provide people with information related to elements. It is organized to show patterns between elements.

5. Is a series of boxes in rows and columns Horizontal row is called a PERIOD (Numbered 1 to 7) Vertical column forms a GROUP or FAMILY (Numbered from 1 to 18)

6. Element Symbol  Large letters in each box show the symbol for the element  Most are an abbreviation derived from the element’s modern chemical name.

7. Some symbols are for the elements Latin name  Some named after the location in which they were discovered (Californium discovered at the University of California  Some named after scientists who made important contributions to their field of study (einsteinium –Albert Einstein) Modern NameSymbolLatin Name CopperCucuprum GoldAuaurum IronFeferrum LeadPbplumbum PotassiumKkalium

8. Atomic Number  Number above the element’s symbol on the left  Shows how many protons are in the nucleus of one atom of the element Therefore the atomic number also tells you how many electrons are in an atom Note: The number of protons equals the number of electrons

9. Atomic Mass  Tells you the total mass of all the protons and neutrons in an atom Mass Number  Represents the sum of the number of protons and neutrons in an atom.

10. Determining the number of Neutrons Mass Number (Atomic Mass) - Atomic Number = Number of Neutrons