The 7 horizontal rows. Period. Example: Period 1 has 2 elements: Hydrogen (H) and Helium (He) Period 2 has 8 elements

Transcription

1 The Periodic Table

2 The 7 horizontal rows Period Example: Period 1 has 2 elements: Hydrogen (H) and Helium (He) Period 2 has 8 elements

3 Group Vertical column of the Periodic Table A group is also called a family of elements because all elements in the same group share some physical and chemical properties

4 Metals Include all members of Groups 1 through 12 as well as some elements of Groups 13 through 16 All metals are good conductors of electricity Conductivity increases as temperature decreases All are solid at room temperature except Mercury

5 Transition Metals Elements in Groups 3 through 12 including the two long rows below the main table Have varied properties Not as reactive as Group 1 and 2 elements

6 Nonmetals Elements in Groups 17 and 18 as well as some members of Groups 14 through 16 Poor conductors of electricity Conductivity increases as temperature increases Can be gases, solids or liquids at room temperature

7 Semiconductors (metalloids) Not in one group but spread across groups starting with Boron, Silicon, Germanium, Arsenic, Antimony and Tellurium Conduct electricity better than nonmetals but not as well as metals Useful in electronic devices Solid at room temperature

8 Lanthanides and Actinides Lanthanides rare earth metals (lanthanum) Actinides radioactive elements (uranium)

9 Group Names Group 1: Alkali Metals (Note Hydrogen is not a metal but it is in group 1) Group 2: Alkali Earth Metals (Be, ) Groups 3 12: Transition Metals Metalloids/Semiconductors: Not in one group but spread across groups starting with Boron, Silicon, Germanium, Arsenic, Antimony and Tellurium

10 Group Names (cont.) Group 17: Halogens (F, Cl, Br, I, ) Group 18: Noble Gases (He, Ne, Ar, ) Lathanides: elements after Lanthanum to Lutetium Actinides: Actinium to Lawrencium

11 6 Atomic #: # of Protons C Element Symbol Carbon Element Name Atomic Mass: # of Protons + # of Neutrons

12 Julius Meyer Used atomic weights to arrange 28 elements into 6 families that had similar chemical and physical properties Incomplete periodic table

13 Dmitri Mendeleev Left gaps (worked on Meyers) Predicted that new elements would be discovered Arranged elements known at the time by similarities in their physical and chemical properties Ordered by increasing atomic mass

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16 Henry Moseley Arranged elements by increasing atomic number Discrepancies disappeared Similar physical and chemical properties occur at regular intervals (periodic law)

17 Moseley (cont.) Moseley s discovery was consistent with Mendeleev s ordering of the periodic table by properties rather than strictly atomic number He showed that there were gaps in the sequence at numbers 43, 61 and 75 (now known to be radioactive, non-naturallyoccurring, technetium and promethium, and the last discovered naturally-occurring element rhenium, respectively)

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19 Periodic Law Periodic Law states: the physical and chemical properties of the elements are periodic functions of their atomic numbers The periodic table is an arrangement of the elements in order of their atomic numbers so the elements with similar properties fall in the same group or column

20 Past to Present The periodic table has changed since Mendeleev s time Chemists have discovered new elements In recent years chemists have synthesized new elements in the laboratory Significant addition to the periodic table was discovery of the noble gases

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