Presentation on theme: "The History and Arrangement of the Periodic Table"— Presentation transcript:
1 The History and Arrangement of the Periodic Table 11/09The History and Arrangement of the Periodic Table
2 History of the Periodic Table 11/09History of the Periodic Table1869 – Dmitri Mendeleev (Russian Chemist) thought elements may have something in common.Organized the elements into a tableMade each element a card and listed its properties known at the time (mass, density, color, melting point and valence number).
3 Dmitri Mendeleev (cont.) 11/09Dmitri Mendeleev (cont.)Mendeleev organized each card (element) according to its atomic massNoticed a repeating pattern of valence numbers (1, 2, 3, 4, 5, etc.)Noticed elements fell into columns (groups or families)Noticed all elements in a column had the same valence number and showed similar physical and chemical properties.
4 Dmitri Mendeleev (cont.) 11/09Dmitri Mendeleev (cont.)Mendeleev left blank spaces in his table so elements would line up – he also predicted what properties the undiscovered elements would have.He predicted properties of five of these elements and their compounds. Three of these missing elements were discovered by others within 15 years.The element, atomic number 101, has been named after Mendeleev.
6 11/09Henry Moseley1913 – Henry Moseley (English Scientist) changed the arrangement of the periodic table.Instead of by increasing atomic mass, it was arranged by increasing atomic number (# of protons).
7 Arrangement of the Periodic Table 11/09Arrangement of the Periodic TableSystematic arrangement of the elementsArranged by atomic number and propertiesNumbered groups/families are in vertical columnsPeriods are by amount of energy levels in horizontal rows (1-7)Divided into regions: metals, nonmetals and metalloids
9 Metals - properties Elements on the left side of the table Good conductors of electricityShinyDuctile – can be drawn into thin wiresMalleable – can be hammered into thin sheets and other shapesHigh melting pointTend to lose electrons
10 Nonmetals - properties Elements to the right of the zigzag on the tableDo not conduct heat or electricityDull in appearance (not shiny)Brittle or break easilyNot ductile or malleable (cannot be drawn into wire or hammered into sheets)Lower densitiesLower melting pointsTend to gain electrons
11 Metalloids - properties Elements that are found along both sides of the zigzag line (except for Al)Properties of both metals and nonmetalsSemiconductors - conduct heat and electricity better than nonmetals but not as well as metalsSolidsCan be shiny or dullBoth ductile and malleable
12 Chemical Groups (Families) 11/09Elements that are in the same group or family (column) of the Periodic Table have similar properties because they have the same number of valence electrons
13 Group (Family) 1 - Alkali Metals 1 valence electron in outer energy levelVery reactive, bond easily with other substances (unstable and explosive)Never found alone in natureSoft, silver-white, shinyEasily lose 1 electron toform a stable +1 ionForm ionic bondsNote:Hydrogen is a nonmetal gas, and forms covalent bonds. So why is it in this Alkali Metal family?
14 Hydrogen is a nonmetal gas and forms covalent bonds Hydrogen is a nonmetal gas and forms covalent bonds So why is it in the Alkali Metal family?The number of valence electrons = 1
15 Group/Family 2 - Alkaline Earth Metals 11/09Group/Family 2 - Alkaline Earth Metals2 valence electrons in outer energy level2nd most reactive elements, bond easily with other substances, unstableNever found alone in natureLose 2 electrons to form stable +2 ionsForm ionic bondsCombine with oxygen and other non-metals in the Earth’s crust
16 Groups 3-12 The Transition Metals 1 or 2 valence electronsCan lose and/or share valence electronsCommon metals – gold, silver & copperForm metallic bondsUnpredictable
17 From Metals to Nonmetals (e- in outer energy level) Group 13 Boron Group/Family 3 valence electronsGroup 14 Carbon Group 4 valence electronsGroup 15 Nitrogen Group 5 valence electronsGroup 16 Oxygen Group 6 valence electronsGroup 17 Halogen Group 7 valence electronsGroup 18 Noble Gases 8 valence electrons* Helium is a Noble Gas but has a full outer shell with 2 valence e-
18 Rare Earth Elements (Inner Transition Metals) 11/09Rare Earth Elements (Inner Transition Metals)First Row –Lanthanide Series- Rare Earth metals- All but one is non-radioactiveSecond Row – Actinide Series- Most are man-made and radioactive- Many are short-lived