Why is the Periodic Table important to me?
• The periodic table is the most useful tool to a chemist.
• You get to use it on every test.
• It organizes lots of information about all the known elements.

Pre­Periodic Table Chemistry ...
• ...was a mess!!!
• No organization of elements.
• Imagine going to a grocery store with no organization!!
• Difficult to find information.
• Chemistry didn’t make sense.

The Periodic Table
Dmitri Mendeleev: Father of the Table
HOW HIS WORKED...
• Put elements in rows by increasing atomic weight.
• Put elements in columns by the way they reacted.
SOME PROBLEMS...
• He left blank spaces for what he said were undiscovered elements. (Turned out he was right!)
• He broke the pattern of increasing atomic weight to keep similar reacting elements together.

The Current Periodic Table
• Mendeleev wasn’t too far off.
• Now the elements are put in rows by increasing ATOMIC NUMBER!!
• The horizontal rows are called periods and are labeled from 1 to 7.
• The vertical columns are called groups are labeled from 1 to 18.

Groups...Here’s Where the Periodic Table Gets Useful!!
• Elements in the same group have similar chemical and physical properties!!
• (Mendeleev did that on purpose.)
Why??
• They have the same number of valence electrons. (we will discuss this tomorrow)
• They will form the same kinds of ions.

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Families/groups Periods
• Columns of elements are called groups or families.
• Elements in each family have similar but not identical properties.
• For example, lithium (Li), sodium (Na), potassium (K), and other members of family IA are all soft, white, shiny metals. • All elements in a family have the same number of valence electrons.
• Each horizontal row of elements is called a period.
• The elements in a period are not alike in properties.
• In fact, the properties change greatly across even given row.
• The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas. Families on the Periodic Table
• Columns are also grouped into families.
• Families may be one column, or several columns put together.
• Families have names rather than numbers. (Just like your family has a common last name.)

Hydrogen
• Hydrogen belongs to a family of its own.
• Hydrogen is a diatomic, reactive gas.
• Hydrogen was involved in the explosion of the Hindenberg.
• Hydrogen is promising as an alternative fuel source for automobiles

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Alkali Metals
• 1st column on the periodic table (Group 1) not including hydrogen.
• Very reactive metals, always combined with something else in nature (like in salt).
• Soft enough to cut with a butter knife

Alkaline Earth Metals
• Second column on the periodic table. (Group 2)
• Reactive metals that are