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Periodicity and the Periodic Table
Vocabulary: Transition Metals Demitri Mendeleev Halogens Noble Gases relative atomic mass Inner Transition Metals periodicity atomic number Lanthanides Actinides periodic law Periods family/group Alkali Metals Alkali Earth Metals MC Escher, ~1950
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What is the periodic table and why is it shaped the way it is?
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Let’s look at some properties of elements. Do you see any patterns?
Lithium Mass: 7 Type: Very reactive solid metal Berylium Mass: 9 Type: Somewhat reactive solid metal Boron Mass: 11 Type: Both metal and nonmetal properties Carbon Mass: 12 Type: Somewhat reactive solid nonmetal Nitrogen Mass: 14 Type: Fairly unreactive gaseous nonmetal Oxygen Mass: 16 Type: Fairly reactive gaseous nonmetal Fluorine Mass: 19 Type: Very reactive gaseous nonmetal Neon Mass: 20 Type: Nonreactive gaseous nonmetal Sodium Mass: 23 Type: Very reactive solid metal Magnesium Mass: 24 Type: Somewhat reactive solid metal Aluminum Mass: 27 Type: Somewhat reactive solid metal Silicon Mass: 28 Type: Both metal and nonmetal properties Phosphorous Mass: 31 Type: Fairly reactive solid nonmetal Sulfur Mass: 32 Type: Fairly reactive gaseous nonmetal Chlorine Mass: 35 Type: Fairly reactive gaseous nonmetal Argon Mass: 40 Type: Nonreactive gaseous nonmetal Potassium Mass: 27 Type: Very reactive solid metal Calcium Mass: 28 Type: Somewhat reactive solid metal
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Do you see any exceptions to those patterns?
Let’s look at some properties of elements: Do you see any patterns now? Lithium Mass: 7 Type: Very reactive solid metal Berylium Mass: 9 Type: Somewhat reactive solid metal Boron Mass: 11 Type: Both metal and nonmetal properties Carbon Mass: 12 Type: Somewhat reactive solid nonmetal Nitrogen Mass: 14 Type: Fairly unreactive gaseous nonmetal Oxygen Mass: 16 Type: Fairly reactive gaseous nonmetal Fluorine Mass: 19 Type: Very reactive gaseous nonmetal Neon Mass: 20 Type: Nonreactive gaseous nonmetal Sodium Mass: 23 Type: Very reactive solid metal Magnesium Mass: 24 Type: Somewhat reactive solid metal Aluminum Mass: 27 Type: Somewhat reactive solid metal Silicon Mass: 28 Type: Both metal and nonmetal properties Phosphorous Mass: 31 Type: Fairly reactive solid nonmetal Sulfur Mass: 32 Type: Fairly reactive gaseous nonmetal Chlorine Mass: 35 Type: Fairly reactive gaseous nonmetal Argon Mass: 40 Type: Nonreactive gaseous nonmetal Potassium Mass: 39 Type: Very reactive solid metal Calcium Mass: 40 Type: Somewhat reactive solid metal Do you see any exceptions to those patterns?
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What is periodicity? In the mid-1800’s, a Russian chemist named Demitri Mendeleev discovered that when the elements were placed in order of increasing relative atomic mass, the chemical and physical properties of the elements repeated periodically.
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What is periodicity? This led to Mendeleev’s organization of the elements into a chart similar to what we now call the periodic table. However, where Mendeleev organized the elements by atomic mass, we now organize them by atomic number (the number of protons each element has) which better matches the periodicity of the elements.
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The Periodic Law Periodic Law: The organization of the elements by increasing atomic number shows that the chemical and physical properties of the elements repeat periodically.
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Families/Groups Columns on the periodic table are known as families or groups. They are numbered 1 – 18 as shown below. Many of the families have names as shown in the key above the periodic table below. You will need to know these family names and locations.
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Families/Groups Families of elements typically have very similar physical and chemical properties (just like people in families typically have similar characteristics!)
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Group: Alkali Metals Alkali Metals: Li Na K Rb Cs
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Group: Halogens Halogens: http://www.youtube.com/watch?v=u2ogMUDBaf4
F Cl Br I
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Group: noble Gases Noble Gases: He Ne Ar Kr Xe
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Periods Rows on the periodic table are known as periods (referring to the periodic law.) They are numbered 1 – 7 as shown below.
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Periods If elements in groups have similar properties, then what can be said about elements in periods?
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