Introduction to the Periodic Table of Elements Seventh Grade Science Some images are from www.chem4kids.com www.middleschoolscience.com

Reading the Periodic Table Each square gives information about the atoms of the element Atomic Number (# of protons) Chemical Symbol Element Name Average Atomic Mass

Arrangement of Periodic Table Elements are arranged in vertical columns , called groups or families, to show similarities in their chemical and physical properties Groups are labeled with a number at the top of their column Each horizontal row is called a period Properties of elements change in a predictable way from one end of the period to the other

Quiz Quickie What information is contained on each square of the periodic table? What do groups on the periodic table show? How do the properties of elements change as you move from left to right on the periodic table?

Periods of the Periodic Table Periods are horizontal rows that move from left to right on the Periodic Table As you read from left to right, one proton and one electron are added from one element to the next element Atomic size decreases as you move across the table Elements on the left side and right side of the table are the least dense Elements in the middle of the table are the most dense Osmium (Os) has the highest known density, located in the center of the table

Groups of the Periodic Table Elements on the periodic table are arranged into families, also known as groups, based on their chemical properties. Each family has a specific name to differentiate it from the other families in the periodic table. Read from top to bottom Elements in each family or group react differently with other elements.

Quiz Time! How are families or groups arranged on the periodic table? What happens to the atomic size as you move from left to right across the periodic table?

ALKALI METALS Group 1 Hydrogen is not a member, it is a nonmetal 1 electron in the outer shell Soft and silvery metals Very reactive, especially with water Conduct electricity Image: http://www.learner.org/interactives/periodic/groups2.html

ALKALINE EARTH METALS Group 2 2 electrons in the outer shell White and malleable Reactive, but less than Alkali Metals Conduct electricity

TRANSITION METALS Groups 3 through 12 Good conductors of heat and electricity Some are used for jewelry The transition metals are able to put up to 32 electrons in their second to last shell Can bond with many elements in a variety of shapes

Check for Understanding What are some characteristic properties of elements in the Alkali Metals group or family? How do the Alkaline Earth Metals differ from the Alkali Metals? What characteristic do the Alkali, Alkaline Earth and Transition Metals have in common?

Metalloids Metalloids are shown on either side of the zigzag line of the table Usually depicted as purple in color Have properties of both metals and nonmetals Silicon (Si) is the most common metalloid Make up semiconductors found in electronic devices

BORON FAMILY Group 13 3 electrons in the outer shell Most are metals Boron is a metalloid

CARBON FAMILY Group 14 4 electrons in the outer shell Contains metals, metalloids, and a nonmetal Carbon (C)

NITROGEN FAMILY Group 15 5 electrons in the outer shell Can share electrons to form compounds Contains metals, metalloids, and nonmetals

OXYGEN FAMILY Group 16 6 electrons in the outer shell Contains metals, metalloids, and nonmetals Reactive

Quiz Quickie! How does the number of electrons affect the element’s reactivity? What do the Boron, Carbon, Nitrogen, and Oxygen families have in common? What is a metalloid and where are they located?

Halogens Group 17 7 electrons in the outer shell All are nonmetals, except Astatine (At) Very reactive Often bonded with Group 1 elements

Noble Gases Group 18 Exist as gases Nonmetals 8 electrons in the outer shell = Full Helium (He) has only 2 electrons in the outer shell = Full Not reactive with other elements

Rare Earth Metals Also known as Lanthanide and Actinide Series Some are radioactive Silver, silvery-white, or gray metals. Conduct electricity

Checking for Understanding Why are the Noble Gases considered to be unreactive? What is it about the Halogen family that makes the elements within that family so reactive? Where are the Rare Earth Metals located with regard to the periodic table?