Vocabulary and Notes 8th grade Science The Periodic Table Vocabulary and Notes 8th grade Science Power points are for you to use it you want. Feel free to edit to fit your classroom.

Vocabulary Physical property – observable characteristics of matter without it changing into something else (density, melting point) Chemical property – observed when matter interacts with other matter (flammability) Atomic mass – average mass of 1 atom of an element Symbol –one or two letters that stand for an element Group – elements in a column in the Periodic Table Periods – horizontal row of the Periodic Table

History of Periodic Table 1830 – have 55 elements and no idea of atomic numbers Did feel that elements could be organized in some manner 1860 –Dimitri Mendeleev discovered system Was a Russian scientist, wrote facts about elements on cards and organized cards Noticed patterns appearing when organization based on increasing atomic mass Portrait of Dimitri Mendeleyev by Ilya Repin

Organization Atomic numbers increase from left to right and top to bottom Elements with same properties were placed in the same group (vertical column) – also known as a family Family name based on first element in column When placed in order of atomic mass and properties didn’t match - new group created Have 18 groups or vertical columns –numbered 1 thru 18 Left spaces if needed, confident that elements would be discovered that fit group and properties

Organization cont. Each horizontal row called a period Have 7 periods – part of periods 6 & 7 have been separated out and appear as rows below main section – keeps table from being too wide Can predict physical and chemical properties based on where the element is located on table

Periodic Table

Square in Periodic Table Square for each element usually includes atomic number, symbol, name, and atomic mass Sometimes will have other information depending on the table 20 Ca calcium 40.08

Let’s Look at Some Groups in the Periodic Table

Metals 75% of elements considered metals Are good conductors of electricity and heat Are very reactive – most form compounds very easily by giving up valence electron (s) Easily combine to form alloys Are malleable and ductile

Group 1 The Alkali Metals Known as alkali metals- most reactive family Are soft, silver-gray, light weight Melting points decrease as you go down the group Melt at low temperatures Have 1 electron in outer shell which makes them very reactive When put in H2O some will explode

Group 2 The Alkaline Earth Metals 2nd most reactive group Have 2 electrons in outer shell – are generally found combined with other elements When mixed in a solution will produce a solution with ph > 7 This is why called alkaline or base metals

Transition Metals Include a lot of elements Group has many electrons and will share them in many ways Able to put up to 32 electrons in second to last shell- which is the maximum Able to use last 2 outer most shells for bonding which makes them have a wide variety of properties

Group 7 Halogens Have 7 electrons in outer shell – makes them as reactive as alkali metals Often bonds with metals and elements in group1 Less reactive as go down the chart

Inert Gases Called noble gases Least reactive of all as have full outer shells Rarely combine with other elements – called inert As you move down the family gases become rarer Used all over world in signs, balloons, headlights, etc.

Lanthanides Considered rare-earth metals Found naturally on earth Only one is radioactive

Actinides All radioactive Some not found in nature – are made only in high tech laboratories and do not last very long

Two Special Cases Hydrogen and Helium Most abundant element in universe Occurs as molecule of two atoms – H2 A lot of Earth’s H found in water (H20) Is colorless, odorless, tasteless gas Low density Is a nonmetal Forms compounds with many other elements Not assigned to any group Helium Part of noble gases –but only has 2 electrons in outer shell 2nd most abundant element on Earth Is rare due to atoms being so light they escape from the atmosphere Is found where there is natural gas (mostly in Texas) Is twice as dense as H and is nonflammable Has lowest boiling point of any substance and does not freeze unless pressure is applied

Lab Activity The Missing Person See hand-out

Additional Activities Video - The Periodic Table Activity - Fabulous Periodic Eggs Lab – Understanding and Using the Periodic Table Activity - Element Scrabble Worksheet – The Periodic Table Element Cards Web Quest

Credits Textbook – Science Explorer Grade 8 Prentice Hall Textbook – Chemistry – Molecule, Matter, and Changes – Atkins, Peter and Jones, Loretta Website -http://www.chem4kids.com/files/elem_pertable.html